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通过电子克隆技术从陆地棉中分离了一个Gh MYC4基因(Gen Bank登录号:KF751654),该基因编码的蛋白属于b HLH类转录因子。生物信息学分析结果显示:该基因完整开放阅读框有1 650 bp,编码549个氨基酸。Gh MYC4蛋白的N-端具有MYC蛋白家族特有的b HLH-MYC-N保守结构域,C端具有高度保守的DNA结合域即b HLH结构域。同源比对和系统进化树分析结果显示Gh MYC4蛋白与陆地棉b HLH转录因子和可可b HLH转录因子的亲缘关系最近,与其他物种的MYC2家族成员具有很大的相似性。通过Real time-PCR检测该基因的组织表达特异性,结果显示该基因在陆地棉的根部和叶片中高效表达,纤维中微量表达。在拟南芥原生质体中进行该基因的瞬时表达,证实了Gh MYC4蛋白定位于细胞核。转Gh MYC4的拟南芥受到高盐和干旱胁迫后相比于对照在表型上表现出很好的抗旱耐盐性能,其叶片相对含水量、可溶性糖含量及脯氨酸含量显著高于对照,MDA含量显著低于对照。该结果为培育抗旱耐盐棉花新品种提供了新的基因来源。
A Gh MYC4 gene (GenBank accession number: KF751654) was isolated from upland cotton by electronic cloning technique and the protein encoded by this gene belongs to bHL class transcription factor. Bioinformatics analysis showed that the complete open reading frame of this gene was 1 650 bp, encoding 549 amino acids. The Gh MYC4 protein has a b HLH-MYC-N conserved domain specific to the MYC protein family at its N-terminus and a highly conserved DNA-binding domain, b HLH domain, at its C-terminus. Homology comparison and phylogenetic tree analysis showed that Gh MYC4 protein has the closest genetic relationship with b HLH transcription factor and cacao b HLH transcription factor, and has similarities with MYC2 family members of other species. The specific expression of this gene was detected by Real time-PCR. The results showed that the gene was highly expressed in the roots and leaves of upland cotton and was expressed in the fiber. Transient expression of this gene in Arabidopsis protoplasts confirmed that Gh MYC4 protein localized to the nucleus. The Arabidopsis thaliana transformed with Gh MYC4 showed good drought resistance and salt tolerance phenotype compared with the control under high salt and drought stress, and its relative water content, soluble sugar content and proline content were significantly higher than those of the control , MDA content was significantly lower than the control. This result provided a new gene source for breeding new varieties of drought-resistant and salt-resistant cotton.