The Regulation And Mechanism Of ABA On Maize Kernel Growth And Development

Plant hormone abcisic acid(ABA)is generally regarded as a very sensitive signal produced during abiotic stress,such as drought,and plays a key role on maize kernel growth and development.To investigate the regulatory mechanism of ABA on kernel growth during the grain-filling stage,maize hybrids(Zhengdan 958,Denghai 605)were carried with different concentrations of ABA(0,5,10,100?M in vitro culture at the early and middle post-pollination stages,and grew in large waterproof sheds and pots with incomplete pollination on ears under different water-deficit treatments during the grain grain-filling stage.The main research results are as follows:1.In vitro culture with different concentrations of ABA application at early-and post pollination stages,the results indicated that a significantly elevated ABA under exogenous ABA applied,and kept a high level with high ABA application.When ABA was applied at the early post-pollination stage,weight loss was observed in ABA treatments,especially reduced remarkably with high concentration,mainly attributed to the decrease of sink capacity(inhibition endosperm cell)and sink activity(affect soluble acid invertase(SAI)and acid cell wall invertase(CWI)activities).When ABA was applied at the middle post-pollination stage,kernel weight was observably reduced with high concentration and mildly increased with low concentration,which was regulated due to sink activity.The mild stimulatory effect of low concentration on sucrose synthase(SS),ADP-glucose pyrophosphorylase(AGPase)and starch synthase(SSS)activities,accompanying the kernel weight increase,were noted,but no significant.In addition,weight loss from similarly high ABA concentrations applied at the early post-pollination stage was considerably obvious compared with that of the middle post-pollination stage,but neither led to kernel abortion under the condition of in vitro culture.2.To investigate the interaction of ABA and CTK on kernel growth at the early stage in vitro culture.The results indicated that CTK alleviated the inhibitory effect on endosperm cell division of ABA,and the degree of alleviation was related to the concentration of CTK in the mixed treatment,ultimately,CTK could rescue the ABA inhibitory effect on kernel weight,however,CTK could not alter the cell structure destroyed of ABA.In addition,the effects of ABA and CTK on the development of kernel were further studied by transcriptome sequencing and proteomics.It was found that starch and glucose metabolism,hormone signal and secondary metabolic process were involved in the growth and development of kernels with different treatments.In the process of grain growth and development,the mechanism of the hormones interaction still needs further study.3.Under different drought stress treatments during the early-pollination stage,it showed that the grain weight of the two cultivars decreased with different degree with complete pollination treatments,especially the apical kernel of Denghai 605 compared with Zhengdan 958,whereas these phenomena were altered under an incomplete pollination treatment,which indicated that the carbohydrate played an important role in the grain growth and development,and also demonstrate that the maize apical kernel has the clear potential capacity to regulate its development.The proteomics was applied to further study the apical kernel growth under severe drought,for Zhengdan 958,the metabolism of carbohydrate and the regulation of 14-3-3 protein and GAPDH maybe play a major role in kernel growth in response to water-deficit,regulating starch accumulation and the ultimate weight of maize kernels;for Denghai 605,the metabolism of sugar and post-transcriptional level mainly involved in the kernel growth in response to water-deficit.In addition,the regulation mechanism of kernel growth and development under drought stress still needs further study.4.The results showed that the maximum and mean grain-filling rate were decreased with ABA treatments at the early post-pollination stage,and reduced with high ABA concentration while increased with low concentration at the middle stage.Furthermore,the grain weight of the same hybrid was significantly positively correlated with the mean grain-filling rate and the increased grain weight of early,middle and late stages,and the grain weight of different maize hybrids Zhengdan 958 and Denghai 605 was determined by grain-filling rate and duration.In addition,ABA promoted starch synthesis,primarily induced ADP-glucose pyrophosphorylase activity,accelerates grain dehydration,and shortens the grain-filling period,leading to precocious grain maturation at the two stages,and an obvious effect at the middle post-pollination stage.It is an important way to keep a high or stable yield with precocious grain maturation by selecting the suitable cultivar with appropriate ABA concentration or gentle drought during the middle or later grain-filling stage.