甘蔗ASR基因家族鉴定及逆境胁迫响应分析

Genome-wide identification of the ASR gene family and analysis of its expression pattern under various stress conditions in sugarcane

摘要:

脱落酸、胁迫及成熟诱导蛋白(abscisic acid, stress and ripening-induced protein, ASR)是一类在植物成熟诱导和逆境胁迫响应过程中发挥重要作用的蛋白质。尽管ASR蛋白已在多种植物中被鉴定，但其在甘蔗中的研究仍较为有限，其结构特征与功能机制尚不清晰。为此，本研究拟在全基因组水平系统鉴定甘蔗ASR基因家族成员，解析其分子特征与进化关系，并探究其在生长发育及逆境胁迫下的表达模式。结果显示，从甘蔗(Saccharum spp.)栽培种‘R570’和野生种割手密(Saccharum spontaneum)中分别鉴定出40个ShASR和15个SsASR基因，所有成员均包含典型的ABA/WDS结构域。结合水稻ASR蛋白构建系统发育树，可将甘蔗ASR蛋白划分为3个亚家族。理化性质与亚细胞定位预测显示，甘蔗ASR蛋白多为稳定、亲水性蛋白，主要定位于细胞核。进一步分析其基因结构、复制类型与染色体分布发现，ASR基因主要通过全基因组或片段重复事件扩增，并在染色体上呈亚家族聚集分布。启动子区域富含胁迫响应、激素响应及生长发育相关的顺式作用元件。转录组分析表明，多数ASR基因在甘蔗5个组织(叶、叶鞘、蔗皮、蔗肉和蔗芽)中均有表达，并受黑穗病菌侵染和干旱胁迫诱导。实时荧光定量PCR结果显示，外源激素及黑穗病菌处理后，ShASR1、ShASR6、ShASR14、ShASR20、ShASR25和ShASR40等基因表达显著变化，提示其可能参与调控甘蔗的胁迫响应、抗病性及生长发育过程。本研究系统解析了甘蔗ASR基因家族的特征与功能，为甘蔗抗逆分子育种提供了理论基础与候选基因资源。

Abstract:

Abscisic acid, stress and ripening-induced (ASR) proteins play crucial roles in plant ripening induction and stress responses. Although ASR proteins have been identified in various plant species, systematic studies in sugarcane remain limited, and their structural and functional characteristics are poorly understood. To this end, this study aimed to systematically identify members of the sugarcane ASR gene family at the genome-wide level, elucidate their molecular characteristics and evolutionary relationships, and investigate their expression patterns during growth, development, and stress responses. The results showed that a total of 40 ShASR genes from the Saccharum spp. cultivar ‘R570’ and 15 SsASR genes from the wild species Saccharum spontaneum were identified. All the predicted ASR proteins contained the characteristic ABA/WDS domain. Phylogenetic analysis, using rice ASR proteins as a reference, classified the sugarcane ASRs into three distinct subfamilies. Physicochemical property predictions indicated that sugarcane ASR proteins were stable and hydrophilic, mainly localized to the nucleus. Further analyses of gene structures, duplication patterns, and chromosomal distribution revealed that ASR genes mainly expanded through whole-genome or segmental duplication events and exhibited subfamily-specific clustering on chromosomes. Promoter analysis showed enrichment of cis-acting elements related to stress and plant hormone responses, as well as growth and development. Transcriptomic data revealed that most ASR genes were expressed in sugarcane leaf, leaf sheath, pith, skin, and bud samples and were responsive to smut pathogen infection and drought stress. RT-qPCR results confirmed that six ShASR genes (ShASR1, ShASR6, ShASR14, ShASR20, ShASR25, and ShASR40) showed differential expression patterns in response to exogenous plant hormone treatments and smut pathogen challenge. These findings suggested that ShASR genes might play important roles in regulating stress responses, disease resistance, and development in sugarcane. This study provides a comprehensive understanding of the sugarcane ASR gene family and offers valuable genetic resources for molecular breeding of stress-tolerant sugarcane cultivars.