Arabidopsis thaliana L. yellow variegated （var2） mutant is defective in a chloroplast FtsH family metalloprotease, AtFtsH2/VAR2, and displays an intriguing green and white leaf variegation. This unique var2-mediated...Arabidopsis thaliana L. yellow variegated （var2） mutant is defective in a chloroplast FtsH family metalloprotease, AtFtsH2/VAR2, and displays an intriguing green and white leaf variegation. This unique var2-mediated leaf variegation offers a simple yet powerful tool for dissecting the genetic regulation of chloroplast development. Here, we report the isolation and characterization of a new var2 suppressor gene, SUPPRESSOR OF VARIEGA TION8 （SVR8）, which encodes a putative chloroplast ribosomal large subunit protein, L24. Mutations in SVR8 suppress var2 leaf variegation at ambient temperature and partially suppress the cold-induced chlorosis phenotype of var2. Loss of SVR8 causes unique chloroplast rRNA processing defects, particularly the 23S-4.5S dicistronic precursor. The recovery of the major abnormal processing site in svr823S-4.5S precursor indicate that it does not lie in the same position where SVR8/L24 binds on the ribosome. Surprisingly, we found that the loss of a chloroplast ribosomal small subunit protein, $21, results in aberrant chloroplast rRNA processing but not suppression of var2 variegation. These findings suggest that the disruption of specific aspects of chloroplast translation, rather than a general impairment in chloroplast translation, suppress var2variegation and the existence of complex genetic interactions in chloroplast development.展开更多
Leaf variegation,the mosaic of colors on the leaf surface,can be developed by certain plant species without external influence.Although it may be associated with a variety of functions,the stable existence of differen...Leaf variegation,the mosaic of colors on the leaf surface,can be developed by certain plant species without external influence.Although it may be associated with a variety of functions,the stable existence of different leaf color morphs within a plant species has not been fully explained by previous studies.This study focuses on the two leaf morphs of Cypripedium forrestii,an endangered lady slipper orchid,and compares their micromorphological structure,photosynthetic potential,differentially expressed genes(DEGs),and ecological features to gain a comprehensive understanding of the underlying leaf variegation polymorphism.Our findings demonstrate that leaf variegation is not pathological and does not affect photosynthetic potential.Additionally,it significantly reduces herbivory damage.We found that the probability of herbivory and leaf area loss for variegated leaves was notably higher under drought conditions.Therefore,variegated individuals may be more adaptive under such conditions,while non-variegated ones may be more cost-effective in normal years.These results suggest that different leaf color morphs may be favored by varying environmental conditions,and leaf polymorphism may be a legacy of ancient climate and herbivore fluctuations.展开更多
Maize leaves are produced from polarized cell divisions that result in clonal cell lineages arrayed along the long axis of the leaf. We utilized this stereotypical division pattern to identify a collection of mutants ...Maize leaves are produced from polarized cell divisions that result in clonal cell lineages arrayed along the long axis of the leaf. We utilized this stereotypical division pattern to identify a collection of mutants that form chloroplast pigmentation sectors that violate the clonal cell lineages. Here, we describe the camouflage1 （cfl） mutant, which develops nonclonal, yellow-green sectors in its leaves. We cloned the cfl gene by transposon tagging and determined that it encodes porphobilinogen deaminase （PBGD）, an enzyme that functions early in chlorophyll and heme biosynthesis. While PBGD has been characterized biochemically, no viable mutations in this gene have been reported in plants. To investigate the in vivo function of PBGD, we characterized the cfl mutant. Histological analyses revealed that cfl yellow sectors display the novel phenotype of bundle sheath cell-specific death. Light-shift experiments determined that constant light suppressed cfl sector formation, a dark/light transition is required to induce yellow sectors, and that sectors form only during a limited time of leaf development. Biochemical experiments determined that of 1 mutant leaves have decreased PBGD activity and increased levels of the enzyme substrate in both green and yellow regions. Furthermore, the cfl yellow regions displayed a reduction in catalase activity. A threshold model is hypothesized to explain the cfl variegation and incorporates photosynthetic cell differentiation, reactive oxygen species scavenging, and PBGD function.展开更多
The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmenta...The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.展开更多
基金supported by funds from National Natural Science Foundation of China to F.Y. (31071073 31170219) and to X.L. (31100864)+2 种基金by Chinese Ministry of Education Program of New Century Excellent Talents in University (NCET 09 0657) to F.Yby funding to S.R. from the US Department of Energy Energy Biosciences panel (DE FG02 94ER20147)
文摘Arabidopsis thaliana L. yellow variegated （var2） mutant is defective in a chloroplast FtsH family metalloprotease, AtFtsH2/VAR2, and displays an intriguing green and white leaf variegation. This unique var2-mediated leaf variegation offers a simple yet powerful tool for dissecting the genetic regulation of chloroplast development. Here, we report the isolation and characterization of a new var2 suppressor gene, SUPPRESSOR OF VARIEGA TION8 （SVR8）, which encodes a putative chloroplast ribosomal large subunit protein, L24. Mutations in SVR8 suppress var2 leaf variegation at ambient temperature and partially suppress the cold-induced chlorosis phenotype of var2. Loss of SVR8 causes unique chloroplast rRNA processing defects, particularly the 23S-4.5S dicistronic precursor. The recovery of the major abnormal processing site in svr823S-4.5S precursor indicate that it does not lie in the same position where SVR8/L24 binds on the ribosome. Surprisingly, we found that the loss of a chloroplast ribosomal small subunit protein, $21, results in aberrant chloroplast rRNA processing but not suppression of var2 variegation. These findings suggest that the disruption of specific aspects of chloroplast translation, rather than a general impairment in chloroplast translation, suppress var2variegation and the existence of complex genetic interactions in chloroplast development.
基金supported by:Science&Technology Basic Resources Investigation Program of China for Survey and Germplasm Conservation of PSESP in Southwest China(2017FY100100)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0502)+1 种基金the PSESP project of Yunnan Forestry and Grassland Bureau(2021SJ14X-09)and the project“Collection and Conservation of Plant Species with Extremely Small Populations of Polystichum glaciale and Cypripedium forrestii in Lijiang”(2021SJ14X-11).
文摘Leaf variegation,the mosaic of colors on the leaf surface,can be developed by certain plant species without external influence.Although it may be associated with a variety of functions,the stable existence of different leaf color morphs within a plant species has not been fully explained by previous studies.This study focuses on the two leaf morphs of Cypripedium forrestii,an endangered lady slipper orchid,and compares their micromorphological structure,photosynthetic potential,differentially expressed genes(DEGs),and ecological features to gain a comprehensive understanding of the underlying leaf variegation polymorphism.Our findings demonstrate that leaf variegation is not pathological and does not affect photosynthetic potential.Additionally,it significantly reduces herbivory damage.We found that the probability of herbivory and leaf area loss for variegated leaves was notably higher under drought conditions.Therefore,variegated individuals may be more adaptive under such conditions,while non-variegated ones may be more cost-effective in normal years.These results suggest that different leaf color morphs may be favored by varying environmental conditions,and leaf polymorphism may be a legacy of ancient climate and herbivore fluctuations.
文摘Maize leaves are produced from polarized cell divisions that result in clonal cell lineages arrayed along the long axis of the leaf. We utilized this stereotypical division pattern to identify a collection of mutants that form chloroplast pigmentation sectors that violate the clonal cell lineages. Here, we describe the camouflage1 （cfl） mutant, which develops nonclonal, yellow-green sectors in its leaves. We cloned the cfl gene by transposon tagging and determined that it encodes porphobilinogen deaminase （PBGD）, an enzyme that functions early in chlorophyll and heme biosynthesis. While PBGD has been characterized biochemically, no viable mutations in this gene have been reported in plants. To investigate the in vivo function of PBGD, we characterized the cfl mutant. Histological analyses revealed that cfl yellow sectors display the novel phenotype of bundle sheath cell-specific death. Light-shift experiments determined that constant light suppressed cfl sector formation, a dark/light transition is required to induce yellow sectors, and that sectors form only during a limited time of leaf development. Biochemical experiments determined that of 1 mutant leaves have decreased PBGD activity and increased levels of the enzyme substrate in both green and yellow regions. Furthermore, the cfl yellow regions displayed a reduction in catalase activity. A threshold model is hypothesized to explain the cfl variegation and incorporates photosynthetic cell differentiation, reactive oxygen species scavenging, and PBGD function.
文摘The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.
