| Idesia polycarpa Maxim.var.vestita Diels is an excellent woody oil plant,and its fruits,dried fruits and seeds contain a large amount of oil,which is known as the "oil bank on trees".However,the difficulty of germination caused by seed dormancy has restricted the industrial cultivation and utilization of Idesia polycarpa.Dormancy is a complex trait determined by genetic and environmental factors,and it is an ecological adaptation of plant seeds to resist unfavorable conditions,and the mechanisms of its formation are therefore diverse.The aim of this study was to investigate the types of dormancy in Idesia polycarpa and to find the best method to break dormancy,and to investigate the regulatory mechanisms of seeds in the process of dormancy release by combining transcriptomics and a series of indicators of physiological changes that occur in Idesia polycarpa seeds during the process of dormancy release.The main experimental results are as follows:(1)By investigating the effects of temperature and light on seed germination,it was found that the seeds of Idesia polycarpa are light-demanding seeds with an optimal germination temperature of 25°C.The seeds were subjected to water uptake assay,and it was found that the seeds did not have water uptake barriers,implying that Idesia polycarpa seeds were not physically dormant.By observing its anatomical structure,it was found that the seeds of Idesia polycarpa had an intact embryo,representing the absence of morphological dormancy.1 m M gibberellin(GA3,Gibberellin)was able to increase the germination rate of seeds,but its maximum germination rate was only 60%;the germination rate as well as germination rate increased significantly after 30 d of cold lamination(4/10°C),and the germination rate was higher than 90%.This indicates that the seeds of Idesia polycarpa have shallow physiological dormancy,and lamination is the best method to break seed dormancy.The results of the physiological indexes showed that the soluble sugar content in the seeds accumulated gradually with the lamination process,the amylase activity in the seeds increased,the content of two types of macromolecular stores,starch and protein,decreased during the lamination process,and the content of fat also decreased with the lamination process in combination with the previous experimental results.This indicates that the three types of macromolecular stores in the seeds are broken down into small molecules as the lamination progresses and participate in various metabolic cycles in the body to provide energy for the release of seed dormancy,which is conducive to the release of seed dormancy and provides sufficient energy for subsequent germination.(2)Six periods of Idesia polycarpa: dry seeds(WT),laminar 30 d(KO),early germination after laminar 30 d(KI),complete germination after laminar 30 d(KU),1 m M GA3 treatment when germination rate reached 40%(OE),and blank control when germination rate reached 15%(OR)were taken as materials for transcriptomic analysis.The experimental results showed that in the process of seed dormancy release under lamellar treatment(WT,KO,KI,KU),the KO stage had a large inhibitory effect on abscisic acid(ABA,Abscisic Acid)synthesis,and the expression of ZEP and NCED,the key enzymes regulating ABA synthesis,was down-regulated 5-fold,although the gene encoding CYP707 A,a key enzyme for ABA catabolism,was down-regulated 2-fold,but decomposition rate is low,its synthesis rate is even lower,i.e.,with the lamellar treatment,the content of ABA inside the seeds will gradually decrease and the inhibition of seed germination is weakening,which is conducive to breaking seed dormancy.It was further found that the inhibition of ABA synthesis at the KO stage was about twice that at the OE stage,which could possibly be one of the reasons for the superiority of the laminar treatment over the exogenous hormone treatment.Consistent with the results of previous physiological experiments,the germination rate of seeds under the laminar treatment could reach about 90% and could completely break seed dormancy,while the exogenous hormone treatment could promote germination,but the germination rate was less than 60%and could not completely break seed dormancy.The expression of key enzymes for the synthesis of seed germination-promoting hormones such as growth hormone(IAA,Indole-3-aceticacid),jasmonic acid(JA,Jasmonic acid),brassinolide(BR,Brassinolide),and ethylene(ETH,Ethylene)was up-regulated under both treatments.The two macromolecular stores,starch and protein,were found to be decreasing with lamination,and the soluble sugar content increased as well as the amylase activity,consistent with the data from transcriptome analysis.genes related to key enzymes regulating the pathway of catabolism of these macromolecular stores were expressed twice as much in the OE stage as in the KO stage,and the rate of catabolism was faster in the OE stage.In contrast,genes related to key enzymes regulating metabolic pathways such as pentose phosphate pathway(PPP,Pentose phosphate pathway),glycolytic pathway(EMP,EmbdenMeyerhof-Parnas pathway),and oxidative phosphorylation(OPP)were expressed at KO The expression of genes related to key enzymes of metabolic pathways such as KO stage was more than twice as much as that of OE stage,and the energy supply at KO stage was faster and more,while the energy demand was high before seed germination,i.e.seed dormancy release process,which may be one of the reasons for better laminar treatment.In summary,the seeds of Idesia polycarpa have shallow physiological dormancy,and lamination at 4/10℃ is the best method to break its dormancy;during the lamination process,the content of macromolecular storage inside the seeds gradually decreases,the sugar content increases and the amylase activity rises to meet the energy demand during the whole process and prepare for subsequent germination,which is of great benefit to release seed dormancy;exogenous hormones can promote seed dormancy to a certain extent but The expression of genes regulating ABA synthesis in the seeds was downregulated during lamination,and the expression of key regulatory genes of GA and other promoting hormones IAA and JA was up-regulated;the inhibition of ABA synthesis in the seeds by lamination treatment was stronger than that by exogenous hormone treatment,and the expression of key enzymes of various metabolic pathways was more than twice as much as that by exogenous hormone treatment;it showed that 4/10℃ low temperature lamination and The regulation of various hormones plays an important role in the dormancy release and germination process of seeds of Idesia polycarpa. |
