An Analysis of The Hormones, Antioxidant Enzymes Activities under Drought Stress And Genomic-Wide Analysis of NAC Genes Family in Soybeans (Glycine max L.Merr.)

【摘要】：Soybean(Glycine max L. Merr.) is one of the most prominent legume crops playing significant role in world's food security. Water stress is one of the most severe constraints on crop production. Present study investigated the effects of drought stress imposed for various periods on antioxidant activities and hormones biosynthesis in(drought treated) and control(non-drought treated), four Soybeans(Glycine max L. Merr.) cultivars viz.,(jindou 74, jindou 78) as drought tolerant and(H228, B217) as drought sensitive. Considerable variations in the behavior of antioxidants were observed under drought stress in all Soybeans cultivars. Exposure of plant to drought stress considerably increase MDA concentrations in leaves of all cultivars, and such an increment was more in drought sensitive cultivars. The ROS were scavenged by the enhanced activities of enzymatic(SOD, CAT, POD and APX) antioxidants in response to drought stress with the passage of time; therefore, maximum values for these attributes were observed at 8 days of drought for all cultivars. These antioxidant activities were higher in drought tolerant cultivars as compared to drought-sensitive cultivars at various time points. Moreover, Activities of hormones(ABA, IAA, JA and SA) biosynthesis were enhanced with the passage of time. Data depicted that drought stress substantially affected the hormone levels in all Soybean cultivars. Variations were apparent among cultivars regarding their response to drought stress. The(jindou 74, jindou 78) drought tolerant cultivars remained superior to sensitive cultivars regarding hormone levels and antioxidant activities. In summary, our results are suggested that manipulation of these antioxidants and hormones may lead to improvement in drought stress tolerance.Generally, one of the largest groups of plant-specific transcription factors is NACs proteins, [(NAM) no apical meristem, [ATAF1/2] Arabidopsis transcription activation factor and(CUC2) cup-shaped cotyledon] which play a vital role in plant growth, development and adaption to the environmental conditions. Due to multidimensional role of NAC proteins, it is very import to identify and characterize this proteins family in soybean. In present study, 139 Gm. NACs genes were identified and analyzed, phylogenetic tree was constructed, genes structures, genome localizations, domain duplications and genes expression summaries in soybean. The phylogenic analysis revealed that the NACs genes could be categorized broadly into 18 groups. The chromosomal localizations and genome duplication indicated 139 Gm. NACs contained 747 homologues and distributed across 20 chromosomes. There were similar genes structures in conformity with Gm. NACs groups between 190 and 678 in protein sequences lengths(average length 362.7). The motifs composition of Gm. NACs was highly conserved within the same group. Most of the significantly affected genes by drought were concentrated on chromosome 6 based on transcriptomic changes evaluation by digital gene expression(DGE) in hairy roots. Furthermore, Gm.NAC005, Gm.NAC020, Gm.NAC070 and Gm.NAC117 demonstrated significantly higher expression changes under drought treatments via quantitative real-time PCR(RT-qPCR) analyses. Taken together, 139 NACs genes in Soybean were identified with a careful investigation of their location, structure, duplication, and evolution. Likewise, some groups have evolved, resulting in high levels of functional divergence. Interestingly, Gm. NACs genes respond differently to drought stress which indicates the importance of this gene family in abiotic stress conditions and may be helpful in understanding the complex mechanisms of drought stress.