| Wheat(Triticum aestivum L.)is one of the three important food crops in the world,which provides the main source of food for human beings.With the increase of population and the decrease of arable land,increasing the yield of wheat and other crops can effectively alleviate this contradiction.The utilization of heterosis in wheat can greatly increase the yield of wheat,in which nuclear-cytoplasmic male sterility is one of the important ways to realize the utilization of heterosis in wheat.However,under the background of different Aegilops cytoplasm,the grains of wheat nuclear-cytoplasmic male sterile lines and F1 hybrids had different degrees of shrinkage.Revealing the mechanism of grain shrinkage of wheat nuclear-cytoplasmic male sterile lines and hybrids is helpful to solve the limitation of the application of nuclear-cytoplasmic male sterile lines in production.In this study,different types of isonuclear and heteronuclear male sterile lines and their corresponding maintainer lines were used as materials,and the grain endosperm development caused by abnormal seed development of male sterile lines was taken as the starting point.The phenotype,dry matter accumulation,starch characteristics and the changing trend of α-amylase activity in the later stage of grain development were systematically studied,and the Ta-FLO16 B gene regulating endosperm starch synthesis was cloned.In order to further reveal the molecular mechanism of grain shrinkage of heterocytoplasmic wheat nuclear-cytoplasmic male sterile lines,the relationship between Ta-FLO16 B and starch synthesis in male sterile lines during seed development was explored by corresponding molecular biological methods.The main results obtained are as follows:1.The appearance,cross-cutting and longitudinal cutting of grains in the process of grain development were observed by stereomicroscope.the results showed that,compared with the maintainer line,the wrinkled grains of heterocytoplasmic male sterile lines showed slight shrinkage at the initial stage of development,the starch arrangement in the endosperm was loose and the contents were not full,and obvious shrinkage appeared after water loss in the mature stage.the results showed that the dry matter accumulation and1000-grain weight of grains were determined.The dry matter accumulation of shrunken grains decreased obviously in the later stage of development,and its 1000-grain weight was lower than that of its parents.There were significant differences in seed shrinkage,dry matter content and 1000-grain weight between isonuclear heteroplasmic male sterile lines and heteroplasmic homonucleic male sterile lines,and the degree of seed shrinkage was mild under P background,especially in male sterile line(P)1236.2.The study on the starch characteristics of heterologous Aegilops cytoplasmic wheat male sterile line and its maintainer line showed that the total starch content of wrinkled grain was lower than that of maintainer line,and most of its starch grains were lenticular,flat and rough.there are micropores or grooves on the surface,and there is no significant difference in the number of starch grains,but there is a significant difference in volume between wrinkled grains and maintainer lines.3.The activity of α-amylase was measured during grain endosperm development,and it was found that the activity of α-amylase in maintainer line appeared at about 22 days after anthesis,and there was only one peak,while the activity of α-amylase in wrinkled grains increased twice(22 days and 32 days after anthesis)or only one peak(32 days after anthesis).The results showed that the activity of α-amylase increased in the mature stage,which led to the degradation of part of the starch,which led to the shrinkage of the grain in the later stage of water loss.4.According to the rice gene sequence,the FLO16 gene regulating endosperm starch synthesis was cloned in wheat.The gene has an open reading frame 1065 bp,encodes 333 aa,predicted molecular weight is 35.48549 KDa,isoelectric point p I is 5.75,and has a conserved domain domain of PLN00135.The phylogenetic relationship between Ta-FLO16 B protein and wheat(T.turgidum),wheat(T.dicoccoides)and wheat(Ae.Tauschii)has the highest homology.Quantitative expression analysis showed that Ta-FLO16 B gene was mainly expressed in grains,and there were significant differences in expression levels between isonuclear heteroplasmic male sterile lines and alloplasmic allogenic male sterile lines.Subcellular localization showed that the gene encoded a cytoplasmic protein... |
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