Abstract:

In order to understand the function of SibHLH19 in foxtail millet,the CDS sequence and promoter sequence of SibHLH19 gene were separately cloned with the leaf cDNA and genomic DNA from resistance material Shilixiang as template by PCR.Promoter cis-acting elements and biological characteristics were analyzed using bioinformatics online tools.Then the expression patterns of SibHLH19 in different tissues and during the process to rust resistance were surveyed by qRT-PCR,respectively.Lastly the prokaryotic expression characteristics for the gene were detected by SDS-PAGE,laying a theoretical foundation for further research on SibHLH19 gene function and disease resistance mechanism.The results showed that the CDS sequence of the SibHLH19 transcription factor was 843 bp in length,encoding a total of 280 amino acids,the predicted protein molecular weight was 29.97 ku.The theoretical isoelectric point was 5.85,and the encoded protein chemical formula was C₁₂₉₆H₂₀₇₁N₃₉₇O₄₀₀S₁₁,containing a bHLH conserved domain,belonging unstable hydrophilic protein.The largest element of the protein's secondary structure was random coils,and the smallest element was a β-turn.Evolutionary analysis showed that SibHLH19 had the higher homology to the amino acid sequences of Panicum miliaceum (RLM85279.1),Panicum hallii (PUZ71581.1)and Panicum virgatum (XP_039835205.1),and had the lowest homology with Triticum aestivum(KAF7059972.1)and Aegilops tauschii subsp.strangulata (XP_040244423.1).The analysis of the promoter cis-acting elements showed that there were multiple response elements such as hormones and stresses in the promoter region of the SibHLH19 gene.Tissue expression analysis showed that the gene was mainly expressed at the seedling stage with the highest expression in the aboveground part,and was almost no expression at the booting stage.Within 24 hours of the response to the biotic stress of rust disease in foxtail millet,the SibHLH19 gene expression was up-regulated at 8 and 16 h in the disease resistance response,while its expression was only slightly up-regulated at 16 h and down-regulated at the rest of the time points in the susceptible response.It was speculated that SibHLH19 played a positive regulatory role in the resistance response to rust disease in foxtail millet.The constructed prokaryotic expression vector pET30a-SibHLH19 could express the SibHLH19 fusion protein with an apparent molecular weight of about 44 ku after being induced by 0.1 mmol/L IPTG.

Key words: Foxtail millet, Foxtail millet rust, bHLH transcription factor, Gene expression, Disease resistance