Physiological Response And Transcriptome Profiling Of Gannanzao Navel Orange To Drought Stress

Gannanzao navel orange is a bud variety of Newhall navel orange,and its physiological response mechanism under drought stress is still unclear.In this study,Gannanzao navel orange and Newhall navel orange poncirus trifoliate rootstocks were used as experimental materials,and the physiological and biochemical indexes related to drought stress in leaves of the two plants were measured in different drought days,and the drought resistance of the two plants was compared.subsequently,transcriptome sequencing was used to screen differentially expressed genes in Gannanzao navel orange responding to drought stress.It is of great significance to explore the physiological response of Gannanzao navel orange under drought stress and dissect its drought tolerance molecular mechanism as well as to single out candidate genes that could be used in breeding new cultivars with enhance drought tolerance.The main results were as follows:1.Under natural drought stress Drought experiment in pot,the net photosynthetic rate,stomatal conductance and transpiration rate of Gannanzao navel orange were higher than that of Newhall navel orange,indicating that the photosynthetic capacity of Gannanzao navel orange was stronger than that of Newhall navel orange under natural drought stress.2.Based on the changes of physiological and biochemical indexes of drought-challenged leaves from Gannanzao navel orange and Newhall navel orange,with the development of drought stress,the stomatal closure time of Gannanzao navel orange was earlier than that of Newhall navel orange,which indicated that drought stress had little effect on stomata of Gannan early navel orange;the relative electrolyte leakage and the content of malondialdehyde in the former were significantly lower than in the later,indicating that the membrane system of Gannanzao navel orange was less damaged by drought than that of Newhall navel orange.The changes of carotinoid contents and peroxidase and superoxide dismutase activities indicated that Gannanzao navel orange responded more quickly to drought stress.Gannanzao navel orange was more tolerant to oxidative stress caused by drought.3.RNA-Seq was performed with the leaves of Gannanzao navel orange and Newhall navel orange under drought stress for 0 days,10 days and 20 days.Totally,130.98 Gbp clean reads were obtained,comparing with 0 days.There were totally3942 differentially expressed genes were identified in 1 days of Gannanzao navel orange,and 3304 differentially expressed genes were identified in 5 days.Newhall navel orange totally 236 differentially expressed genes were identified in 1 days,and2041 differentially expressed genes were identified in 5 days.4.GO enrichment analysis showed that differentially expressed genes were mainly enriched to metabolic process,molecular Function,membrane part,catalytic activity.comparing with 0 days.The differentially expressed gene KEGG was mainly enriched to transportation and catabolism,folding,classification and degradation,glycan biosynthesis and metabolism,energy metabolism in Gannanzao navel orange10 days,20 days and Newhall navel orange 20 days.KEGG is not enriched in membrane transport replication and repair,cofactor and vitamin metabolism,polysaccharide biosynthesis and metabolism of Newhall navel orange 10 days.5.1488 transcription factors from 48 transcription factors familie were identified in RNA-Seq data of Gannanzao navel orange and Newhall navel orange.Among the identified differentially expressed genes,13 genes were related to ABA signal pathway,10 genes related to GA signal pathway,30 genes related to ROS,23 genes related toproline synthesis and metabolism and 17 genes related to Photosystem.