Post-anthesis Drought Affects The Physiological Characteristics And Gene Expression Profiles Of Carbon-nitrogen Metabolism And Analysis Of In Maize

The late growth stage is a key period for maize growth,it is more sensitive to drought stress.The distribution of nutrients at the late growth stage is an important factor affecting nutrient use efficiency under drought stress.The experiments were carried out in a rainproof shelter to simulate post-anthesis drought stress in 2015 and 2016.“Zhengdan 958”was selected as plant material.Through the determination of maize yield,accumulation of dry matter and carbon and nitrogen assimilation,combined with key enzyme activities and related gene expression of carbon and nitrogen metabolism between different organs,and analyzed the bioinformatics of carbon and nitrogen metabolism pathways.Investigate the effects of post-anthesis drought on distribution of carbon and nitrogen assimilate in maize.The main conclusions are as follows:1.The results showed that PD stress significantly increased the partitioning rate of dry matter in the ear-leaves and stems during maturity,and the harvest indexes were decreased by4.8%and 14.1%in 2015 and 2016,respectively.The proportion of nitrogen in grain was significantly decreased under PD stress,and the nitrogen distribution ratio decreased by1.88%and 5.29%in two years,respectively.Under PD stress,the content of soluble sugar in the stem,ear-leaves and grains decreased significantly,while the sucrose content in the grains increased significantly.PD stress significantly reduced The C/N ratio in grains,and the C/N ratio of grain was decreased 0.38 and 1.3 in 2 growth season from 2015 and 2016.2.At 35 DAS,the SS activity in grains were higher than well watered treatment under PD stress.From 35 to 50 DAS,the activities of ADP-glucose pyrophosphorylase and starch synthase activity were increased in the ear-leaves and grains under PD stress.At 50 DAS,the ADP-glucose pyrophosphorylase and starch synthase activity in ear-leaves were higher than well watered treatment under PD stress.At 35 DAS,the GS activity of ear-leaves was significantly higher in PD stress than well watered treatment.But there was no significant difference of GS activity in grain between two treatments.The relative expression levels of carbon and nitrogen metabolism key enzyme genes?ZmSh1,ZmAgp1,ZmSSIIa,and ZmGln1-3?have similar trends with their activity.3.RNA-seq results showed that there were 4013 differentially expressed genes in leaves under two water treatments at 50 DAS,of which 2367 genes were up-regulated and 1646were down-regulated under PD stress.Metabolic pathway analysis of differential genes showed that 6 out of 7 genes encoding photosystems?PSI and PSII?reaction center subunits were down regulated under PD stress.The gene encoding the ATP synthase subunit had the strongest reduction level?log₂FC=-8.20?under PD stress.In the pathway of sucrose metabolism,most genes encoding amylase were significantly up-regulated,the expression of SPS and SS genes were significantly up-regulated.In the amino acid metabolic pathway,the most significantly up-regulated gene among these DEGs was L-allo-threonine aldolase?log₂FC=3.59?.Under PD stress,three genes encoding cysteine synthetase were significantly down-regulated.The results showed that PD stress may promote the catabolism of carbon and nitrogen in leaves at the late growth stage,and the content of carbon and nitrogen assimilate was decreased,this lead to leaf presenility.It can be seen that PD stress the late growth stage affects the expression of genes in many major metabolic pathways,which may control the utilization and distribution of carbon and nitrogen assimilation at the late growth stage through affecting the key genes of carbon and nitrogen metabolism and related enzyme activities in leaves.