| Wheat,maize and rice are known as three major food crops in the world.At present,the hybrids of rice and maize have been extensively planted,and have achieved remarkable economic benefit.Meantime,they have made important contribution to world food security.However,the utilization of wheat heterosis,affected by various factors,still stayed at trial stage of small area,which are quite far away from application,is a word problem.The comprehensive comparison of various male sterile lines,the male sterility line induced by chemical hybridization agents,having the advantages of short production cycle,wide select range of parents,and high rate of highly heterotic combinations,turned to have a wide application prospect.At present,relying on the chemical hybrid agent SQ-1,our group developed and integrated a rounded system on hybrid wheat production,and get a series of new varieties of hybrid wheat named“Xiza series”,such as“Xiza No.1”,“Xiza No.5”,“Xiza No.7”and“Xiza No.9”.However,due to the high cost of chemical hybrid SQ-1,it was necessary to study the molecular mechanism on wheat male sterility induced by chemical hybridization agent SQ-1,and based on which to further develop new high-effective,safe and cheap chemical hybridization agents to cut the cost of production.To elucidate the mechanism of pollen abortion in male sterility induced by SQ-1,we will discuss the relation among pollen grain structure,material?starch?distribution,metabolic components and starch synthesis pathways and the pollen abortion induced by SQ-1 in this study.First of all,the plant phenotypic and pollen fertility of sterile lines were observed.Meantime,their anther wall and pollen structure were observed by scanning electron microscope and transmission electron microscope.Secondly,the distribution of nutrient substance?starch?in pollen cells and tapetal cells were detected using semi-thin sectioning and cytochemistry staining.Then the metabolic components were analyzed by Non-targeted metabolomics at different stage in anther development.At last,the key enzyme genes related to starch synthesis pathway were detected by qRT-PCR technique.The main results were as follows:1.The male sterility rate of Xinong 1376 induced by 5kg.ha-1 SQ-1 at Feek's 8.5 was more than 99%,but the plant phenotype of Xinong 1376 wasn't impacted.The anthers of PHYMS-1376 were shriveled,no starch accumulation in pollen grains,and the development of nucleus was slow,most of them stayed at binucleate stage.Meanwhile,the nuclei of PHYMS-1376 pollen developed more slowly with forming abnormal sperm cells in mature pollen having only one or two nuclei.In addition,comparing to Xinong 1376,the inner surface of anther wall of PHYMS-1376 were wrinkled,and there were more residual materials.And the intine and amyloplast were not formed in PHYMS-1376 pollen.2.Comparing to 1376,the tapetum cells of the PHYMS-1376 expanded at the tetrad stage,and degraded earlier,but part ramined residual at binucleate stage,the pollen grains showed a significant decrease at all the stages.Besides,the insoluble polysaccharide in anthers of PHYMS-1376 showed a deline trend from tetrad stage to trinucleate stage,meantime,there was no starch accumulation in pollen grains in both binucleate and trinucleate stages.3.The results of Non-targeted metabolomics study on the stages of anther development of 1376 showed that there were 120 differential metabolite had participated in the development of wheat anther,involving 7 metabolic pathways,including glucose metabolism,lipid metabolism and amino acid metabolism etc.,which mainly involved in glycolysis and TCA cycle.4.Comparing to 1376,there were 131 differential metabolites involved with the pollen abortion of PHYMS-1376,mainly including 24 amino acids,3 fatty acid,1 nucleotides,39organic acid,2 phosphoric acid,17 sugar,11 polyol and 29 other metabolites.There were 251?positive and negative?correlativity among 93 differential metabolites?maximum positive correlation was 0.980 between Glucose-6-phosphate and Fructose-6-phosphate,maximum negative correlation was-0.843 between Noradrenaline and 2-Deoxytetronic acid?.Furthermore,the metabolic pathway analysis showed that these 131 metabolites also participated in 7 metabolic pathways,referring to glycolysis and TCA cycle,in which the normal anther development of 1376 involved,to varying degree.Among them,there were most referrd metabolites in glucose metabolism pathways,including fructose,Fructose-6-phosphate,glucose,Glucose-6-phosphate and sucrose.5.Due to the significant difference between the substance content of glucose metabolism and starch synthesis during the anther development of PHYMS-1376 and 1376,the gene expression of key enzyme activity in composing starch involved in anther abortion were detected by qRT-PCR.The results showed that,comparing to 1376,the gene expression of the key enzymes?ADPGase,GBSS,SSS,SBE and DBE?involved in starch synthesis was variated,and most gene expression significantly reduced in anther.Among them,the low expression of GBSS?and SBE?were particularly prominent during the binucleate and trinucleate stages of sterile lines.Based on these results,the male sterility of wheat induced by chemical hybrid agent SQ-1,may due to the disturb on the metabolites supply and accumulation in anther development,thus there were no starch accumulation in pollen grain and no intine formation,eventually led to pollen abortion. |
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