Plastome variation,including single spontaneous nucleotide substitutions and single insertions/deletions,is the major source of leaf variegation in plants.Additionally,one recent study has showed that a simple plastom...Plastome variation,including single spontaneous nucleotide substitutions and single insertions/deletions,is the major source of leaf variegation in plants.Additionally,one recent study has showed that a simple plastome structural variation,which is induced by one pair of small inverted repeats,can also result in leaf variegation.Here we show a complex plastome structural variation caused by intermolecular and intramolecular recombination across three pairs of small inverted repeats accounts for leaf variegation in a widely cultivated shrub Heptapleurum ellipticum(Araliaceae).This plastome structural variation contains two deletions and two duplications,resulting in dramatic expansion of IRs,substantial contraction of LSC and loss of 11 genes that essential for photosynthesis.Plastome heteroplasmy was detected in both green and albino sectors of variegated leaves.Relative to green sectors,albino sectors in the variegated leaves exhibit significantly reduced expression for the 11 genes lost in the mutated plastome as well as 26 other genes,but significantly increased expression for one gene related to translation apparatus.Optical and transmission electron microscopy observations showed that mesophyll cells of albino sectors possess plastids lacking grana lamellae,which likely carry the mutated plastome and contribute to albinism.In both sectors,the first layer of spongy mesophyll cells beneath the lower epidermis contains normal chloroplasts,suggesting periclinal division of the lower epidermis during development.Our study demonstrates that multiple small repeats can collectively mediate intra-and inter-molecular recombination in plastome and offers a new mechanism accounting for leaf variegation in plants.展开更多
A cell line, SHK, was derived from the kidney of spotted halibut Verasper variegates. The cell line was subcultured more than 40 passages in minimum essential medium （MEM） supplemented with fetal bovine serum （FBS...A cell line, SHK, was derived from the kidney of spotted halibut Verasper variegates. The cell line was subcultured more than 40 passages in minimum essential medium （MEM） supplemented with fetal bovine serum （FBS） and 10 ng ml4 basic fibroblast growth factor （bFGF）. Cell morphology from primary culture and subculture was observed continuously by microscopy. The SHK cell line consisted predominantly of fibroblast-like cells. The cell line was able to grow between 20℃ and 30℃ with the optimum growth at 24℃ and with a reduced growth between 12℃ and 20℃. The growth rate of the cells increased as the proportion of FBS increased from 10% to 20% at 28℃ with optimum growth at the concentration of 20%. The doubling time of the cells was determined to be 44.8 h. Chromosome analysis revealed that 52% of the SHK cells maintained a normal diploid chromosome number （2n=46）. The cells were successfully transfected with green fluorescent protein （GFP） reporter plasmids and the expression of GFP gene in the cells indicated the possible utility of the cells in gene expression studies. The cells were infected by lymphosystis disease virus （LCDV） and found to be susceptible to the virus in cytopathic effect （CPE） observation. The infection was confirmed by PCR and electron microscopy experiments, which proved the existence of the viral particles in the cytoplasm of the virus-infected cells.展开更多
基金supported financially by the National Natural Science Foundation of China(31811530297 and 32170217).
文摘Plastome variation,including single spontaneous nucleotide substitutions and single insertions/deletions,is the major source of leaf variegation in plants.Additionally,one recent study has showed that a simple plastome structural variation,which is induced by one pair of small inverted repeats,can also result in leaf variegation.Here we show a complex plastome structural variation caused by intermolecular and intramolecular recombination across three pairs of small inverted repeats accounts for leaf variegation in a widely cultivated shrub Heptapleurum ellipticum(Araliaceae).This plastome structural variation contains two deletions and two duplications,resulting in dramatic expansion of IRs,substantial contraction of LSC and loss of 11 genes that essential for photosynthesis.Plastome heteroplasmy was detected in both green and albino sectors of variegated leaves.Relative to green sectors,albino sectors in the variegated leaves exhibit significantly reduced expression for the 11 genes lost in the mutated plastome as well as 26 other genes,but significantly increased expression for one gene related to translation apparatus.Optical and transmission electron microscopy observations showed that mesophyll cells of albino sectors possess plastids lacking grana lamellae,which likely carry the mutated plastome and contribute to albinism.In both sectors,the first layer of spongy mesophyll cells beneath the lower epidermis contains normal chloroplasts,suggesting periclinal division of the lower epidermis during development.Our study demonstrates that multiple small repeats can collectively mediate intra-and inter-molecular recombination in plastome and offers a new mechanism accounting for leaf variegation in plants.
基金supported by grants from State 863High-Technology Rand Project of China(2006AA09Z406,2006AA10A401)Taishan Scholar Project of Shan-dong Province
文摘A cell line, SHK, was derived from the kidney of spotted halibut Verasper variegates. The cell line was subcultured more than 40 passages in minimum essential medium （MEM） supplemented with fetal bovine serum （FBS） and 10 ng ml4 basic fibroblast growth factor （bFGF）. Cell morphology from primary culture and subculture was observed continuously by microscopy. The SHK cell line consisted predominantly of fibroblast-like cells. The cell line was able to grow between 20℃ and 30℃ with the optimum growth at 24℃ and with a reduced growth between 12℃ and 20℃. The growth rate of the cells increased as the proportion of FBS increased from 10% to 20% at 28℃ with optimum growth at the concentration of 20%. The doubling time of the cells was determined to be 44.8 h. Chromosome analysis revealed that 52% of the SHK cells maintained a normal diploid chromosome number （2n=46）. The cells were successfully transfected with green fluorescent protein （GFP） reporter plasmids and the expression of GFP gene in the cells indicated the possible utility of the cells in gene expression studies. The cells were infected by lymphosystis disease virus （LCDV） and found to be susceptible to the virus in cytopathic effect （CPE） observation. The infection was confirmed by PCR and electron microscopy experiments, which proved the existence of the viral particles in the cytoplasm of the virus-infected cells.
