Table_2_Transcriptomic analysis reveals mechanisms for the different drought tolerance of sweet potatoes.xlsx

Drought is a common environmental stress with great negative impacts on plant growth, development and geographical distribution as well as agriculture and food production. Sweet potato is characterized by starchy, fresh and pigmented tuber, and is regarded as the seventh most important food crop. However, there has been no comprehensive study of the drought tolerance mechanism of different sweet potato cultivars to date. Here, we studied the mechanism for drought response of seven sweet potato drought-tolerant cultivars using the drought coefficients, physiological indicators and transcriptome sequencing. The seven sweet potato cultivars were classified into four groups of drought tolerance performance. A large number of new genes and transcripts were identified, with an average of about 8000 new genes per sample. Alternative splicing events in sweet potato, which were dominated by first exon and last exon alternative splicing, were not conserved among different cultivars and not significantly affected by drought stress. Furthermore, different drought-tolerance mechanisms were revealed through differentially expressed gene analysis and functional annotation. Two drought-sensitive cultivars, Shangshu-9 and Xushu-22, mainly resisted drought stress by up-regulating plant signal transduction. The other drought-sensitive cultivar Jishu-26 responded to drought stress by down-regulating isoquinoline alkaloid biosynthesis and nitrogen/carbohydrate metabolism. In addition, the drought-tolerant cultivar Chaoshu-1 and drought-preferred cultivar Z15-1 only shared 9% of differentially expressed genes, as well as many opposite metabolic pathways in response to drought. They mainly regulated flavonoid and carbohydrate biosynthesis/metabolism in response to drought, while Z15-1 increased photosynthesis and carbon fixation capacity. The other drought-tolerant cultivar Xushu-18 responded to drought stress by regulating the isoquinoline alkaloid biosynthesis and nitrogen/carbohydrate metabolism. The extremely drought-tolerant cultivar Xuzi-8 was almost unaffected by drought stress and responded to drought environment only by regulating the cell wall. These findings provide important information for the selection of sweet potatoes for specific purposes.

干旱是一种常见的环境胁迫（environmental stress），对植物生长、发育、地理分布以及农业与粮食生产均具有显著负面影响。甘薯以其富含淀粉、质地鲜嫩且带有色素的块根为特征，被列为全球第七大重要粮食作物。然而截至目前，针对不同甘薯品种的耐旱机制尚缺乏系统性研究。本研究以7个耐旱甘薯品种为材料，通过干旱系数、生理指标及转录组测序（transcriptome sequencing）技术，解析其干旱响应机制。本研究将7个供试甘薯品种划分为4个耐旱表现类群。研究共鉴定出大量新基因与转录本，每个样本平均鉴定到约8000个新基因。甘薯的可变剪接（alternative splicing）事件以外显子首端与末端可变剪接为主，且不同品种间的可变剪接并不保守，同时其亦不受干旱胁迫的显著影响。此外，本研究通过差异表达基因（differentially expressed gene）分析与功能注释，揭示了不同品种各异的耐旱机制。两个干旱敏感品种‘商薯9号’与‘徐薯22’主要通过上调植物信号转导（signal transduction）通路抵御干旱胁迫。另一个干旱敏感品种‘济薯26’则通过下调异喹啉生物碱（isoquinoline alkaloid）生物合成及氮/碳水化合物代谢通路响应干旱胁迫。此外，耐旱品种‘巢薯1号’与耐旱偏好型品种Z15-1仅共享9%的差异表达基因，且二者响应干旱的代谢通路存在大量反向调控模式。二者均主要通过调控类黄酮（flavonoid）与碳水化合物的生物合成/代谢响应干旱胁迫，而Z15-1还可通过提升光合作用与碳固定能力应对干旱。另一个耐旱品种‘徐薯18’则通过调控异喹啉生物碱生物合成及氮/碳水化合物代谢通路响应干旱胁迫。极端耐旱品种‘徐紫8号’几乎不受干旱胁迫的影响，仅通过调控细胞壁（cell wall）相关通路响应干旱环境。本研究结果可为甘薯的定向选育提供重要理论依据与数据支撑。