Cloning And Functional Verification Of Drought-related NAC Transcription Factor Genes In Sugar Beet

Sugar beet[Beta vulgaris L.)was the main sugar and cash crop in northern China.Drought and water shortage are the main factors restricting the increase of sugar beet yield in northern China.So far,many NAC transcription factors related to drought resistance had been cloned and identified.However,few studies have been reported on the relationship between NAC transcription factor family genes and drought resistance in sugar beet.In present work,NAC transcription factors induced by drought in Sugar beet were explored to provide theoretical basis for elucidating the molecular mechanism of drought resistance in Sugar beet and cultivating new stress-resistant Sugar beet.The main results are as follows:The members of the NAC transcription factor family in sugar beet were identified by using the conserved domain sequence of NAC as the search sequence.The amino acid composition and physicochemical properties,phylogenetic relationship,gene chromosome localization and protein domain conservativeness prediction of the members of the NAC transcription factor family in Sugar beet were analyzed,and the expression pattern of NAC gene were analyzed under drought stress in Sugar beet by RNA-seq and qRT-PCR.The results showed that there were 52 members of NAC family genes in sugar beet,50 members were unevenly distributed on 9 chromosomes and 2 were not localized in present.The number of amino acid residues encoding NAC family genes ranged from 48 to 711,17 members were alkaline proteins and 4 members were hydrophilic proteins.52 members could be divided into two categories,38 in category Ⅰ,14 in category Ⅱ.The number of exons and introns was highly variable,and 23 genes were up-regulated in the NAC family of sugar beet under drought stress.Drought resistance related genes in sugar beet NAC gene family were analyzed by RNA-scq and qRT-PCR,and two drought resistance candidate genes were cloned.The complete CDS fragments of Bvjtwcis and Bv_hdfh genes were cloned from the drought-resistant Sugar beet(HI0466),and their lengths were 1095 bp and 912 bp,respectively.The base sequence of CDS region of Bv_hdfh gene is consistent with genomic data,while there are nine base differences between CDS region and genomic sequence of Bv_twas gene.The heterologous overexpression of Bv_twas and Bv_hdfh increased the root length and number of lateral roots of transgenic lines in transgenic Arabidopsis thaliana under drought stress,and the above-ground of transgenic plants was better than that of wild type under different drought stress;Under the transgenic Arabidopsis leaves,the activities of SOD and CAT were higher than those of wild type,while the relative conductivity was lower than that of wild type,but no significant difference was observed in POD activity.