Mutations and rearrangements of mitochondrial genes cause plant cytoplasmic male sterility. It is a significant way to utilize hybrid vigor to enhance crop yield. Ogu cytoplasmic male sterility(CMS) is a natural cytop...Mutations and rearrangements of mitochondrial genes cause plant cytoplasmic male sterility. It is a significant way to utilize hybrid vigor to enhance crop yield. Ogu cytoplasmic male sterility(CMS) is a natural cytoplasmic male sterility type discovered in radishes, being successfully transferred to rapeseed and cruciferous vegetables. However, current studies lack depth in exploring the molecular mechanisms of its male sterility. This study confirmed that orf138 is the causal gene for Ogu CMS through the genetic transformation in Arabidopsis. Transcriptome analysis of aborted anthers in different stages suggested that differentially expressed genes(DEGs) are mainly enriched in pathways such as glycerophospholipid metabolism and arginine and proline metabolism. It reveals that key genes involved in lipid metabolism pathways are significantly down-regulated in the sterile line(OguA), including BnaGPAT1, localized within the tapetum mitochondrial and endoplasmic reticulum. This could lead to changes in the metabolism of substances like acylglycerols within the tapetum, causing disruptions in lipid metabolism. This is consistent with morphological and subcellular structural changes in the tapetum and microspore cells, as observed in the transmission electron microscopy. This abnormal lipid metabolism may trigger specific reactive oxygen species(ROS) accumulation in an oxidative stress response, ultimately leading to an aborted microspore. Our study based on transcriptome has deepened our understanding of the molecular mechanisms in Ogu CMS.展开更多
Male gametes are produced in the anthers and are essential for fertilization and seed setting.A transverse section of the anther reveals four layers:the epidermis,endothecium,middle layer,and tapetum.The tapetum,being...Male gametes are produced in the anthers and are essential for fertilization and seed setting.A transverse section of the anther reveals four layers:the epidermis,endothecium,middle layer,and tapetum.The tapetum,being the innermost layer,plays a critical role in supplying nutrients,enzymes,and protection to microspores.Detailed microscopic and ultrastructural analyses have revealed highly active and well-organized structures within the tapetum,referred to as tapetal organelles.Molecular studies have highlighted the significance of tapetal cell death and the nurturing role of the tapetum for microspores.However,the mechanisms by which these processes are mediated by tapetal organelles at the cellular level remain elusive.The discovery of mutants defective in tapetal organelles has enabled further investigations into their structure,morphology,and function.This review discusses the molecular and functional roles of various tapetal organelles,such as plastids(amyloplasts and elaioplasts),mitochondria,tapetosomes,endoplasmic reticulum,and lipid bodies.We provide an overview of their roles,highlight key organelles in the tapetum,and address recent challenges and potential applications of genes regulating tapetal organelles in enhancing crop fertility.展开更多
The present work presents an iin silicoi analysis of Upstream Regulatory Modules (URMs) of genes expressed in tapetum specific manner in dicotyledon and monocotyledon plants. In the current analysis, we identified sev...The present work presents an iin silicoi analysis of Upstream Regulatory Modules (URMs) of genes expressed in tapetum specific manner in dicotyledon and monocotyledon plants. In the current analysis, we identified several motifs conserved in these URMs of which ten were observed to be part of known icisi-elements using tools and databases like MEME, PLACE, MAST and TFSEARCH. We also identified that binding sites for two transcription factors, DOF and WRKY71 were found to be present in majority of the URMs.展开更多
As a complex wall system in flowering plants, the pollen outer wall mainly contains aliphatic sporopollenin; however, the mechanism for synthesizing these lipidic precursors during pollen development remains less well...As a complex wall system in flowering plants, the pollen outer wall mainly contains aliphatic sporopollenin; however, the mechanism for synthesizing these lipidic precursors during pollen development remains less well understood. Here, we report on the function of the rice tapetum-expressing TDR （Tapetum Degeneration Retardation） gene in aliphatic metabolism and its regulatory role during rice pollen development. The observations of transmission electron microscopy （TEM） and scanning electron microscopy （SEM） analyses suggested that pollen wall formation was significantly altered in the tdr mutant. The contents of aliphatic compositions of anther were greatly changed in the tdr mutant revealed by GC-MS （gas chromatography-mass spectrometry） testing, particularly less accumulated in fatty acids, primary alcohols, alkanes and alkenes, and an abnormal increase in secondary alcohols with carbon lengths from C29 to C3S in tdr. Microarray data revealed that a group of genes putatively involved in lipid transport and metabolism were significantly altered in the tdr mutant, indicating the critical role of TDR in the formation of the pollen wall. Also, a wide range of genes （236 in total--154 up-regulated and 82 down-regulated） exhibited statistically significant expressional differences between wild-type and tdr. In addition to its function in promoting tapetum PCD, TDR possibly plays crucial regulatory roles in several basic biological processes during rice pollen development.展开更多
In anther development, tapetal cells take part in complex processes, including endomitosis and apoptosis （programmed cell death）. The tapetum provides many of the proteins, lipids, polysaccharides and other molecule...In anther development, tapetal cells take part in complex processes, including endomitosis and apoptosis （programmed cell death）. The tapetum provides many of the proteins, lipids, polysaccharides and other molecules necessary for pollen development. Several transcription factors, including DYT1, TDF1, AMS, MS188 and MS1, have been reported to be essential for tapetum development and function in Arabidopsis thaliana. Here, we present a detailed cytological analysis of knockout mutants for these genes, along with an in situ RNA hybridization experiment and double mutant analysis showing that these transcription factors form a genetic pathway in tapetum development. DYT1, TDF1 and AMS function in early tapetum development, while MS188 and MS1 are important for late tapetum development. The genetic pathway revealed in this work facilitates further investigation of the function and molecular mechanisms of tapetum development in Arabidopsis.展开更多
Glycerol-3-phosphate acyltransferase （GPAT） mediates the initial synthetic step for the formation of glycer- olipids, which act as the major components of biological membranes and the principal stored forms of energ...Glycerol-3-phosphate acyltransferase （GPAT） mediates the initial synthetic step for the formation of glycer- olipids, which act as the major components of biological membranes and the principal stored forms of energy. GPAT6 is a member of the Arabidopsis GPAT family, which is crucial for cutin biosynthesis in sepals and petals. In this work, a func- tional analysis of GPAT6 in anther development and plant fertility was performed. GPAT6 was highly expressed in the tapetum and microspores during anther development. The knockout mutant, gpat6, caused a massive reduction in seed production. This report shows that the ablation of GPAT6 caused defective tapetum development with reduced endoplas- mic reticulum （ER） profiles in the tapetum, which largely led to the abortion of pollen grains and defective pollen wall formation. In addition, pollen germination and pollen tube elongation were affected in the mutant plants. Furthermore, the double mutant analysis showed that GPAT6 and GPAT1 make joint effects on the release of microspores from tetrads and stamen filament elongation. This work shows that GPAT6 plays multiple roles in stamen development and fertility in Arabidopsis.展开更多
Photoperiod-sensitive genic male-sterile （PSGMS） rice （Oryza sativa L.）, a natural mutant found in the rice cultivar Nongken 58, is very useful for the development of hybrid rice cultivars. Despite its widespread ...Photoperiod-sensitive genic male-sterile （PSGMS） rice （Oryza sativa L.）, a natural mutant found in the rice cultivar Nongken 58, is very useful for the development of hybrid rice cultivars. Despite its widespread use in breeding programs, the initial stage of the abortive development of PSGMS rice and the possible cytological mechanisms of pollen abortion have not been determined. In the present study, a systematic cytological comparison of the anther development of PSGMS rice with its normal fertile counterpart is conducted. The results show that pollen abortion in PSGMS rice first occurs before the pollen mother cell （PMC） stage, and continues during the entire process of pollen development until pollen degradation. The abortive process was closely associated with the abnormal behavior of the tapetum. Although tapetum degeneration in PSGMS rice initiates already at the PMC stage, it proceeds slowly and does not complete until the breakdown of the pollen. Such cytological observations were supported by the results of the TUNEL （TdT-mediated dUTP Nick End Labeling） assay, which detects DNA fragmentation resulting from programmed cell death （PCD）, indicating that the premature tapetum degeneration is in the process of PCD.展开更多
Lily was grown worldwide as a fresh cutting flower because of its colorful petals, but its anther contained a large number of pollen grains that cause serious pollen contamination, however, pollen abortion can effecti...Lily was grown worldwide as a fresh cutting flower because of its colorful petals, but its anther contained a large number of pollen grains that cause serious pollen contamination, however, pollen abortion can effectively reduce the level of pollen pollution. Our analysis aims to use cytological observation to detect the critical stage when pollen abortion occurs and to provide comprehensive gene expression information at the transcriptional level. The result showed that pollen abortion in ‘Little Kiss’ began at the mononuclear stage and the callose that covers the microspores failed to degenerate when young pollens were released from the tetrads. In addition, compared with the normally developed one,the tapetum of ‘Little Kiss’ degraded in advance while the degradation of callose was delayed. Furthermore, 103 differentially expressed genes(DEGs) related to the advance degeneration of tapetum cells and callose were found in the expression levels, including 22 transcription factors(TFs). In particular, two β-glucanase genes(endo-1,3(4)-β-glucanase, exo-β-glucanase) responsible for callose degeneration were significantly down-regulated. These results suggested that pollen abortion may occur at mononuclear stage and that early degeneration of tapetum cells resulted in a significant down-regulation of β-glucanase genes. As a result, the callose to cover microspores impedes the formation of pollen walls, which may possibly lead to pollen abortion.展开更多
The indoleacetic-acid-lysine synthetase (iaaL) gene from Pseudomonas syringae subsp. savastanoi was fused to tobacco tapetum-specific expression promoter TA29, and introduced into tobacco. The expression pattern of th...The indoleacetic-acid-lysine synthetase (iaaL) gene from Pseudomonas syringae subsp. savastanoi was fused to tobacco tapetum-specific expression promoter TA29, and introduced into tobacco. The expression pattern of this chimeric gene was studied, and the endogenous indoleacetic acid (IAA) levels in different organs were assayed. The results demonstrated that TA29 promoter was only able to direct the specific expression of iaaL gene in transgenic tobacco anther, and resulted in the decrease of endogenous IAA levels in transgenic tobacco anther. No significant phe-notype variation was observed among the transgenic plants at the whole plant level. However, the percentage of pollen embryogenesis was reduced to 11 % when anthers of the transgenic plants were cultured on the modified hormone-free Nistch H (NH) medium, while those of both CK1 and CK2 (see sec. 1.2.2) were more than 50% ; when the an-thers were cultured on NH medium supplemented with 0. 2 mg/L IAA, the percentage of pollen embryogenesis re-stored to the same level of that of the wild type (up to 55. 7% ). This study demonstrates that the IAA metabolism in anther tapetum cells is of significant importance to the androgenic development in anther culture.展开更多
The Arabidopsis AtMYB103 gene is required for anther development,but whether the homologous gene in rice has the same role is unclear.Sequence analysis indicated that the rice OsMYB103 gene shares a high sequence simi...The Arabidopsis AtMYB103 gene is required for anther development,but whether the homologous gene in rice has the same role is unclear.Sequence analysis indicated that the rice OsMYB103 gene shares a high sequence similarity with AtMYB103.Therefore,we investigated the functional role of OsMYB103 in anther development using an RNAi approach.The OsMYB103 RNA transcript was expressed most abundantly in flowers,specifically in the tapetum,premeiotic pollen mother cells,and meiotic PMCs.OsMYB103-RNAi transgenic lines grew normally during their vegetative phase but displayed reduced male fertility,a phenotype that was associated with downregulated OsMYB103 transcript levels.Expression of OsMS2,an ortholog of the Arabidopsis AtMS2 gene,was also dramatically reduced in the transgenic plants.Knockdown of OsMYB103 led to defects in tapetum development,and most of the microspores in mature anthers lacked exines.Moreover,OsMYB103 could partially rescue the male sterility phenotype of an AtMYB103 knockout mutant ms188.Taken together,these results indicate that OsMYB103 does have an important role in rice tapetum and microspore development.展开更多
Anthers of male sterile line and its maintainer line of Zidao type rice, Yingxiang A and Yingxiang B were studied by cytological methods, such as F-KI staining, silver nitrate staining and paraffin sections, It is fou...Anthers of male sterile line and its maintainer line of Zidao type rice, Yingxiang A and Yingxiang B were studied by cytological methods, such as F-KI staining, silver nitrate staining and paraffin sections, It is found that in Yingxiang A, there are some abnormalities in meiosis, represented by unequal division at the meiotic phase; the abortion of CMS line arises at the meiotic phase and is almost completed at the phase of monomicrospore, but only a tiny amount of aborted mi- crospores are observed; the abortion is complete and thorough, and none normal functional pollens are found; the morphology of aborted pollens is similar to that of typically aborted pollens; the tapetal cells still exist in anthers from the microsporocyte stage to the tetrad stage, but they are abnormally hyperplastic. However, in Yingxiang B, there are no abnormalities in meiosis at the meiotic phase; the tapetal cells exist in anthers before the tetrad stage, but they disappear completely when the pollen are mature. It is indicated that the abortion of CMS Yingxiang line mainly occurs at the meiotic phase, and is basically completed at the phase of monomicrospore. The abortion is probably caused by the abnormally hyperplastic tapetal cells. The abnormalities in tapetal cells may affect the normal development of pollens, resulting in the emergence of abortion. In addition, the abortion in Yingxiang A is complete and thorough, which is of great significance in hybrid breeding.展开更多
基金supported by the National Natural Science Foundation of China (31930032)。
文摘Mutations and rearrangements of mitochondrial genes cause plant cytoplasmic male sterility. It is a significant way to utilize hybrid vigor to enhance crop yield. Ogu cytoplasmic male sterility(CMS) is a natural cytoplasmic male sterility type discovered in radishes, being successfully transferred to rapeseed and cruciferous vegetables. However, current studies lack depth in exploring the molecular mechanisms of its male sterility. This study confirmed that orf138 is the causal gene for Ogu CMS through the genetic transformation in Arabidopsis. Transcriptome analysis of aborted anthers in different stages suggested that differentially expressed genes(DEGs) are mainly enriched in pathways such as glycerophospholipid metabolism and arginine and proline metabolism. It reveals that key genes involved in lipid metabolism pathways are significantly down-regulated in the sterile line(OguA), including BnaGPAT1, localized within the tapetum mitochondrial and endoplasmic reticulum. This could lead to changes in the metabolism of substances like acylglycerols within the tapetum, causing disruptions in lipid metabolism. This is consistent with morphological and subcellular structural changes in the tapetum and microspore cells, as observed in the transmission electron microscopy. This abnormal lipid metabolism may trigger specific reactive oxygen species(ROS) accumulation in an oxidative stress response, ultimately leading to an aborted microspore. Our study based on transcriptome has deepened our understanding of the molecular mechanisms in Ogu CMS.
基金supported by the National Natural Science Foundation of China(Grant Nos.32272191 and 32350410428).
文摘Male gametes are produced in the anthers and are essential for fertilization and seed setting.A transverse section of the anther reveals four layers:the epidermis,endothecium,middle layer,and tapetum.The tapetum,being the innermost layer,plays a critical role in supplying nutrients,enzymes,and protection to microspores.Detailed microscopic and ultrastructural analyses have revealed highly active and well-organized structures within the tapetum,referred to as tapetal organelles.Molecular studies have highlighted the significance of tapetal cell death and the nurturing role of the tapetum for microspores.However,the mechanisms by which these processes are mediated by tapetal organelles at the cellular level remain elusive.The discovery of mutants defective in tapetal organelles has enabled further investigations into their structure,morphology,and function.This review discusses the molecular and functional roles of various tapetal organelles,such as plastids(amyloplasts and elaioplasts),mitochondria,tapetosomes,endoplasmic reticulum,and lipid bodies.We provide an overview of their roles,highlight key organelles in the tapetum,and address recent challenges and potential applications of genes regulating tapetal organelles in enhancing crop fertility.
文摘The present work presents an iin silicoi analysis of Upstream Regulatory Modules (URMs) of genes expressed in tapetum specific manner in dicotyledon and monocotyledon plants. In the current analysis, we identified several motifs conserved in these URMs of which ten were observed to be part of known icisi-elements using tools and databases like MEME, PLACE, MAST and TFSEARCH. We also identified that binding sites for two transcription factors, DOF and WRKY71 were found to be present in majority of the URMs.
文摘As a complex wall system in flowering plants, the pollen outer wall mainly contains aliphatic sporopollenin; however, the mechanism for synthesizing these lipidic precursors during pollen development remains less well understood. Here, we report on the function of the rice tapetum-expressing TDR （Tapetum Degeneration Retardation） gene in aliphatic metabolism and its regulatory role during rice pollen development. The observations of transmission electron microscopy （TEM） and scanning electron microscopy （SEM） analyses suggested that pollen wall formation was significantly altered in the tdr mutant. The contents of aliphatic compositions of anther were greatly changed in the tdr mutant revealed by GC-MS （gas chromatography-mass spectrometry） testing, particularly less accumulated in fatty acids, primary alcohols, alkanes and alkenes, and an abnormal increase in secondary alcohols with carbon lengths from C29 to C3S in tdr. Microarray data revealed that a group of genes putatively involved in lipid transport and metabolism were significantly altered in the tdr mutant, indicating the critical role of TDR in the formation of the pollen wall. Also, a wide range of genes （236 in total--154 up-regulated and 82 down-regulated） exhibited statistically significant expressional differences between wild-type and tdr. In addition to its function in promoting tapetum PCD, TDR possibly plays crucial regulatory roles in several basic biological processes during rice pollen development.
基金supported by grants from the National Natural Science Foundation of China (30925007)Shanghai(11ZR1425800)the State Key Basic Research and Development Program of China (2007CB947600)
文摘In anther development, tapetal cells take part in complex processes, including endomitosis and apoptosis （programmed cell death）. The tapetum provides many of the proteins, lipids, polysaccharides and other molecules necessary for pollen development. Several transcription factors, including DYT1, TDF1, AMS, MS188 and MS1, have been reported to be essential for tapetum development and function in Arabidopsis thaliana. Here, we present a detailed cytological analysis of knockout mutants for these genes, along with an in situ RNA hybridization experiment and double mutant analysis showing that these transcription factors form a genetic pathway in tapetum development. DYT1, TDF1 and AMS function in early tapetum development, while MS188 and MS1 are important for late tapetum development. The genetic pathway revealed in this work facilitates further investigation of the function and molecular mechanisms of tapetum development in Arabidopsis.
基金This work was supported by grants from the National Science Foundation of China，the National Basic Research Program of China，by the Leading Academic Discipline Project of Shanghai Municipal Education Commission
文摘Glycerol-3-phosphate acyltransferase （GPAT） mediates the initial synthetic step for the formation of glycer- olipids, which act as the major components of biological membranes and the principal stored forms of energy. GPAT6 is a member of the Arabidopsis GPAT family, which is crucial for cutin biosynthesis in sepals and petals. In this work, a func- tional analysis of GPAT6 in anther development and plant fertility was performed. GPAT6 was highly expressed in the tapetum and microspores during anther development. The knockout mutant, gpat6, caused a massive reduction in seed production. This report shows that the ablation of GPAT6 caused defective tapetum development with reduced endoplas- mic reticulum （ER） profiles in the tapetum, which largely led to the abortion of pollen grains and defective pollen wall formation. In addition, pollen germination and pollen tube elongation were affected in the mutant plants. Furthermore, the double mutant analysis showed that GPAT6 and GPAT1 make joint effects on the release of microspores from tetrads and stamen filament elongation. This work shows that GPAT6 plays multiple roles in stamen development and fertility in Arabidopsis.
基金Supported in part by the State Key Basic Research and Development Plan of China (2007CB108700)the National Key Project of Functional Genomics of Major Plants and Animals, China
文摘Photoperiod-sensitive genic male-sterile （PSGMS） rice （Oryza sativa L.）, a natural mutant found in the rice cultivar Nongken 58, is very useful for the development of hybrid rice cultivars. Despite its widespread use in breeding programs, the initial stage of the abortive development of PSGMS rice and the possible cytological mechanisms of pollen abortion have not been determined. In the present study, a systematic cytological comparison of the anther development of PSGMS rice with its normal fertile counterpart is conducted. The results show that pollen abortion in PSGMS rice first occurs before the pollen mother cell （PMC） stage, and continues during the entire process of pollen development until pollen degradation. The abortive process was closely associated with the abnormal behavior of the tapetum. Although tapetum degeneration in PSGMS rice initiates already at the PMC stage, it proceeds slowly and does not complete until the breakdown of the pollen. Such cytological observations were supported by the results of the TUNEL （TdT-mediated dUTP Nick End Labeling） assay, which detects DNA fragmentation resulting from programmed cell death （PCD）, indicating that the premature tapetum degeneration is in the process of PCD.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities(Grant No.KYTZ201602)+1 种基金the High Level Talent Project of the Top Six Talents in Jiangsu(Grant No.NY-077)the earmarked fund for germplasm resources of Nanjing Agricultural University(Grant No.KYZZ201920)。
文摘Lily was grown worldwide as a fresh cutting flower because of its colorful petals, but its anther contained a large number of pollen grains that cause serious pollen contamination, however, pollen abortion can effectively reduce the level of pollen pollution. Our analysis aims to use cytological observation to detect the critical stage when pollen abortion occurs and to provide comprehensive gene expression information at the transcriptional level. The result showed that pollen abortion in ‘Little Kiss’ began at the mononuclear stage and the callose that covers the microspores failed to degenerate when young pollens were released from the tetrads. In addition, compared with the normally developed one,the tapetum of ‘Little Kiss’ degraded in advance while the degradation of callose was delayed. Furthermore, 103 differentially expressed genes(DEGs) related to the advance degeneration of tapetum cells and callose were found in the expression levels, including 22 transcription factors(TFs). In particular, two β-glucanase genes(endo-1,3(4)-β-glucanase, exo-β-glucanase) responsible for callose degeneration were significantly down-regulated. These results suggested that pollen abortion may occur at mononuclear stage and that early degeneration of tapetum cells resulted in a significant down-regulation of β-glucanase genes. As a result, the callose to cover microspores impedes the formation of pollen walls, which may possibly lead to pollen abortion.
基金Project supported by the State Key Laboratory of Plant Molecular Genetics.
文摘The indoleacetic-acid-lysine synthetase (iaaL) gene from Pseudomonas syringae subsp. savastanoi was fused to tobacco tapetum-specific expression promoter TA29, and introduced into tobacco. The expression pattern of this chimeric gene was studied, and the endogenous indoleacetic acid (IAA) levels in different organs were assayed. The results demonstrated that TA29 promoter was only able to direct the specific expression of iaaL gene in transgenic tobacco anther, and resulted in the decrease of endogenous IAA levels in transgenic tobacco anther. No significant phe-notype variation was observed among the transgenic plants at the whole plant level. However, the percentage of pollen embryogenesis was reduced to 11 % when anthers of the transgenic plants were cultured on the modified hormone-free Nistch H (NH) medium, while those of both CK1 and CK2 (see sec. 1.2.2) were more than 50% ; when the an-thers were cultured on NH medium supplemented with 0. 2 mg/L IAA, the percentage of pollen embryogenesis re-stored to the same level of that of the wild type (up to 55. 7% ). This study demonstrates that the IAA metabolism in anther tapetum cells is of significant importance to the androgenic development in anther culture.
基金supported by the National Natural Science Foundation of China (30671127 and 30971553)the National Basic Research Program of China (2007CB947600)
文摘The Arabidopsis AtMYB103 gene is required for anther development,but whether the homologous gene in rice has the same role is unclear.Sequence analysis indicated that the rice OsMYB103 gene shares a high sequence similarity with AtMYB103.Therefore,we investigated the functional role of OsMYB103 in anther development using an RNAi approach.The OsMYB103 RNA transcript was expressed most abundantly in flowers,specifically in the tapetum,premeiotic pollen mother cells,and meiotic PMCs.OsMYB103-RNAi transgenic lines grew normally during their vegetative phase but displayed reduced male fertility,a phenotype that was associated with downregulated OsMYB103 transcript levels.Expression of OsMS2,an ortholog of the Arabidopsis AtMS2 gene,was also dramatically reduced in the transgenic plants.Knockdown of OsMYB103 led to defects in tapetum development,and most of the microspores in mature anthers lacked exines.Moreover,OsMYB103 could partially rescue the male sterility phenotype of an AtMYB103 knockout mutant ms188.Taken together,these results indicate that OsMYB103 does have an important role in rice tapetum and microspore development.
文摘Anthers of male sterile line and its maintainer line of Zidao type rice, Yingxiang A and Yingxiang B were studied by cytological methods, such as F-KI staining, silver nitrate staining and paraffin sections, It is found that in Yingxiang A, there are some abnormalities in meiosis, represented by unequal division at the meiotic phase; the abortion of CMS line arises at the meiotic phase and is almost completed at the phase of monomicrospore, but only a tiny amount of aborted mi- crospores are observed; the abortion is complete and thorough, and none normal functional pollens are found; the morphology of aborted pollens is similar to that of typically aborted pollens; the tapetal cells still exist in anthers from the microsporocyte stage to the tetrad stage, but they are abnormally hyperplastic. However, in Yingxiang B, there are no abnormalities in meiosis at the meiotic phase; the tapetal cells exist in anthers before the tetrad stage, but they disappear completely when the pollen are mature. It is indicated that the abortion of CMS Yingxiang line mainly occurs at the meiotic phase, and is basically completed at the phase of monomicrospore. The abortion is probably caused by the abnormally hyperplastic tapetal cells. The abnormalities in tapetal cells may affect the normal development of pollens, resulting in the emergence of abortion. In addition, the abortion in Yingxiang A is complete and thorough, which is of great significance in hybrid breeding.
