| Xanthoceras sorbifolium Bunge is a monoecious plant with monoecious flowers and widely cultivated owing to its high comprehensive utilization value.However,the number of male flowers is much higher than that of female flowers,leading to the low seed yield,which is the main bottleneck for development of industrial-scale seed utilization,and regulating the male-female ratio has become the key to solve the problem.In this study,the key micro RNAs that may affect the sex differentiation of X.sorbifolium were discovered;the changes of mineral elements and nutrients in the buds during the process of sex differentiation of X.sorbifolium were determined;the reference genes suitable for sex differentiation studies of X.sorbifolium were selected.This study provides a reference for sex regulation through molecular techniques in X.sorbifolium,and provides a theoretical basis for increasing seed yield.The main results were as follows:(1)There were obvious differences in pistils and stamens of female and male flower buds when the inflorescence of X.sorbifolium elongated and the flower buds obviously separated.The stamens in male flower developed normally,while the pistil was degraded,the ovule and ovary gradually withered and shrank,and there was no papillary cell on the stigma.The development of the pistil in the female flower was normal,while the stamens aborted.The pollens were vacuolated with no visible nuclei,and the cytoplasm was thin.(2)A total of 1619 conserved mi RNAs(belonging to 34 families)and 219 novel mi RNAs were identified.Among these,the expression of 162 conserved and 14 novel mi RNAs in the 4 s RNA libraries(s RNA libraries of apical buds and lateral buds when the morphological structure of pistil and stamen had not yet shown a difference and began to show significant differences)were significantly different.Among the differentially expressed mi RNAs,1677 putative target genes of 112 mi RNAs were predicted,and these target genes were involved in diverse developmental and metabolic processes.17 mi RNAs were directly associated with flower and gametophyte development,and the carbohydrate metabolism and glycan biosynthesis and metabolism were the two major pathways.The functions of some mi RNAs were confirmed(mi R156,mi R159 and mi R319),and some were complemented(mi R393,mi R396,mi R162,mi R408,mi R2673 and mi R5169).(3)The contents of K,Mn,Cu and Fe elements in male flower were generally higher than those of female flower during the process of sex differentiation.After the pistil and stamen began to abort,the contents of K,Mn,Cu,Fe,and Mg elements gradually increased in the male flower,while decreased in the female flower.At this time,the content of Ca element in male flower began to be higher than that of female flower,and difference increased as the differentiation progressed.The surplus of these 6 mineral elements were beneficial to the formation of male flowers.After the abortion of pistil and stamens,the amounts of starch and soluble sugar consumed by the female flower were much higher than those of male flower with flowers development.High levels of starch and soluble sugar were beneficial for the formation of female flower.(4)The expression levels of the 7 candidate reference genes were obviously different in different tissues.The expressions in female flowers were significantly higher than that in other materials,and the expression in male flowers was at a lower level.UBQ and e IF-4α were the optimal reference genes for sex differentiation process,and EF-1α and GAPDH were the ideal reference genes for different organs. |
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