Morphological And Physiological Changes Of Taxus Chinensis Var.mairei Seeds In Stratification And Analysis Of Transcriptome During Embryo Culture In Vitro

Seed dormancy is a mechanism to prevent seeds from germination in unfavorable seasons when seedling survival rate is low.Seeds choose the right time to germinate by regulating dormancy status according to seasonal conditions.Determining seasonal dynamics of seed dormancy is important for revealing the adaptation of plant regeneration to the environment.We studied seed dormancy status of Taxus chinensis var.mairei,an endangered species in China,under simulating seasonal temperature regimes and analysed the transcriptome of embryo during culture in vitro.(1)The seed coat of Taxus chinensis var.mairei was water permeable,thus the seed dormancy is not caused by the seed coat characteristics,the embryo is small and not fully developed when the seeds were matured.The seed germinated after a period of field stratification,so the seed dormancy type is simple morphophysiological dormancy.(2)After 12 months of treatment with different temperature stratification(except winter temperature),The embryo length,E:S(embryo length: endosperm length)and split rate of Taxus chinensis var.mairei seeds were increasing with the stratification time.After 9 months of field stratification,the embryo length,E:S and seed split rate reached the maximum.(3)ABA content decreased during stratification,but no obvious pattern of GA and IAA contents was observed.Ratios of GA/ABA and IAA/ABA increased during stratification.After 12 months of stratification at different temperatures,the content of ABA in seeds decreased,but the contents of GA and IAA changed insignificantly.The ratio of GA / ABA and IAA/ABA increased during stratification.After 9 months of natural stratification,the ratio of GA/ABA and IAA/ABA of seeds in field reached the maximum.(4)During different stratification treatments,the contents of storage substances in seeds of Taxus chinensis var.mairei changed greatly,the content of soluble protein was increased in the stratification;the content of soluble sugar changed in the form of "W",decreased at first and then increased;the content of starch and fat were decreased.(5)The differences of gene expression during dormancy release and germination of Taxus chinensis var.mairei embryo were analyzed and discussed.A total of 78154 unigenes were obtained by sequencing.During embryo germination of Taxus chinensis var.mairei,the expression of upstream synthetic gene of ABA was not active,but the expression of downstream metabolic gene of ABA was active,and the expression of synthetic gene of GA was active,which indicated that embryo germination of Taxus chinensis var.mairei was related to the degradation of ABA and synthesis of GA.