高粱MYC基因家族序列、表达模式及自然等位变异分析

Characterization of sequences, expression profiling, and natural allelic variation analysis of the MYC gene family in sorghum (Sorghum bicolor)

摘要:

高粱蚜(Melanaphis sacchari)和丝轴黑粉菌(Sporisorium reilianum)侵染高粱，导致其生长发育受阻、产量和品质下降。采用生物信息学分析和分子生物学方法，研究高粱发育过程及病虫发生下的MYC基因表达模式变化与自然等位DNA变异，为选育抗逆、高产和优质高粱品种提供参考。结果表明，高粱基因组含28个MYC基因，不均匀分布在10条染色体上，基本螺旋-环-螺旋_MYC_N (basic helix-loop-helix_MYC_N, bHLH_MYC_N)与螺旋-环-螺旋(helix-loop-helix, HLH)结构域是高粱MYC基因的保守结构域。基因表达分析显示，SbbHLH35.7g在叶片中表达水平最高；SbAbaIn在早期籽粒中表达强；SbMYC2.1g在成熟花粉中表达水平高。在抗、感蚜品系5叶期叶片中，显著诱导表达的是SbAbaIn、SbLHW.4g和SbLHW.2g。SbbHLH35.7g在穗组织表达水平最高，且受丝轴黑粉菌侵染显著诱导表达。SbMYCs启动子区包含脱落酸、水杨酸、茉莉酸甲酯和干旱诱导等相关元件，使其更好地响应逆境胁迫。通过分析全基因组重测序数据，鉴定到SbMYCs关键的单核苷酸多态性(single nucleotide polymorphism, SNP)或插入缺失标记(insertion-deletion, INDEL)变异。SbAbaIn与TIFY结构域蛋白等互作，SbbHLH35.7g与多药剂外泵蛋白(multidrug efflux transporter, MDR)和核转运蛋白(imporin)等互作。高粱蚜和丝轴黑粉菌侵染分别诱导SbAbaIn和SbbHLH35.7g表达，SbAbaIn通过茉莉酸(jasmonic acid, JA)途径诱导相关基因表达，增强抗虫性；SbbHLH35.7g可能通过解毒途径提高抗病性。

Abstract:

Sorghum aphid (Melanaphis sacchari) and head smut fungi (Sporisorium reilianum) infesting sorghum cause delayed growth and development, and reduce yield and quality. This study use bioinformatics and molecular biological approaches to profile the gene expression pattern during sorghum development and under pest infestation, and analyzed the natural allelic DNA variation of sorghum MYC gene family. The findings provide insights for potential application in breeding the stress resistant and high productivity sorghum varieties. The results indicated that there are 28 MYC genes identified in sorghum genome, distributed on 10 chromosomes. The bHLH_MYC_N and HLH domains are the conserved domains of the MYC gene in sorghum. Gene expression analysis showed that SbbHLH35.7g exhibited high expression levels in leaves, SbAbaIn showed strong expression in early grains, and SbMYC2.1g showed high expression levels in mature pollen. In anti-aphid strains at the 5-leaf stage, SbAbaIn, SbLHW.4g and SbLHW.2g were significantly induced in leaves, while SbbHLH35.7g displayed the highest expression level in panicle tissue, which was significantly induced by the infection of head smut. Promoter cis-element analysis identified methyl jasmonate (MJ), abscisic acid (ABA), salicylic acid (SA) and MYB-binding sites related to drought-stress inducibility. Furthermore, genomic resequencing data analysis revealed natural allelic DNA variations such as single nucleotide polymorphism (SNP) and insertion-deletion (INDEL) for the key SbMYCs. Protein interaction network analysis using STRING indicated that SbAbaIn interacts with TIFYdomain protein, and SbbHLH35.7g interacts with MDR and imporin. SbMYCs exhibited temporal and spatial expression patterns and played vital roles during the sorghum development. Infestation by sugarcane aphids and head smut fungi induced the expression of SbAbaIn and SbbHLH35.7g, respectively. SbAbaIn modulated the jasmonic acid (JA) pathway to regulate the expression of defensive genes, conferring resistance to insects. On the other hand, SbbHLH35.7g participated in detoxification reactions to defend against pathogens.