Yan Haifeng, Ma Guohua, Teixeira da Silva Jaime A, Qiu Lihang, Xu Juan, Zhou Huiwen, Wei Minzheng, Xiong Jun, Li Mingzhi, Zhou Shaohuan, Wu Jianming, Tang Xiuhua
Sugarcane Research Institute of Guangxi Academy of Agricultural Sciences, Guangxi Key Laboratory of Sugarcane Genetic Improvement and Key Laboratory of Sugarcane Biotechnology and Genetic Improvement (Guangxi), Ministry of Agriculture, Nanning, China.
Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, China.
Front Genet. 2021 Nov 24;12:744220. doi: 10.3389/fgene.021.744220. eCollection 2021.
NAC (NAM, ATAF1/2, and CUC2) proteins play a pivotal role in modulating plant development and offer protection against biotic and abiotic stresses. Until now, no systematic knowledge of NAC family genes is available for the food security crop, sweet potato. Here, a comprehensive genome-wide survey of NAC domain-containing proteins identified 130 and 144 genes with full length sequences in the genomes of two diploid wild relatives of cultivated sweet potato, and , respectively. These genes were physically mapped onto 15 and 16 chromosomes, respectively. Phylogenetic analysis divided all 274 NAC proteins into 20 subgroups together with NAC transcription factors (TFs) from . There were 9 and 15 tandem duplication events in the and genomes, respectively, indicating an important role of tandem duplication in sweet potato gene expansion and evolution. Moreover, synteny analysis suggested that most NAC genes in the two diploid sweet potato species had a similar origin and evolutionary process. Gene expression patterns based on RNA-Seq data in different tissues and in response to various hormone, biotic or abiotic treatments revealed their possible involvement in organ development and response to various biotic/abiotic stresses. The expression of 36 NAC TFs, which were upregulated in the five tissues and in response to mannitol treatment, was also determined by real-time quantitative polymerase chain reaction (RT-qPCR) in hexaploid cultivated sweet potato exposed to drought stress. Those results largely corroborated the expression profile of mannitol treatment uncovered by the RNA-Seq data. Some significantly up-regulated genes related to drought stress, such as , , , , and especially , which had a conservative spatial conformation with a closely related paralogous gene, , may be potential candidate genes for a sweet potato drought tolerance breeding program. This analysis provides comprehensive and systematic information about NAC family genes in two diploid wild relatives of cultivated sweet potato, and will provide a blueprint for their functional characterization and exploitation to improve the tolerance of sweet potato to abiotic stresses.
NAC（NAM、ATAF1/2和CUC2）蛋白在调控植物发育过程中发挥着关键作用，并为植物抵御生物和非生物胁迫提供保护。截至目前，对于粮食安全作物甘薯，尚无关于NAC家族基因的系统知识。在此，对含NAC结构域的蛋白进行全基因组综合调查，在栽培甘薯的两个二倍体野生近缘种Ipomoea trifida和Ipomoea triloba的基因组中分别鉴定出130个和144个具有全长序列的基因。这些基因分别被物理定位到15条和16条染色体上。系统发育分析将所有274个NAC蛋白与来自拟南芥的NAC转录因子一起分为20个亚组。在Ipomoea trifida和Ipomoea triloba基因组中分别有9次和15次串联重复事件，表明串联重复在甘薯基因扩展和进化中发挥着重要作用。此外，共线性分析表明，这两个二倍体甘薯物种中的大多数NAC基因具有相似的起源和进化过程。基于不同组织中的RNA-Seq数据以及对各种激素、生物或非生物处理的响应的基因表达模式，揭示了它们可能参与器官发育以及对各种生物/非生物胁迫的响应。在暴露于干旱胁迫的六倍体栽培甘薯中，还通过实时定量聚合酶链反应（RT-qPCR）测定了在五个组织中以及响应甘露醇处理而上调的36个NAC转录因子的表达。这些结果在很大程度上证实了RNA-Seq数据所揭示的甘露醇处理的表达谱。一些与干旱胁迫显著上调相关的基因，如IbNAC1、IbNAC2、IbNAC3、IbNAC4，尤其是IbNAC5，其具有保守的空间构象且与一个密切相关的旁系同源基因IbNAC6相似，可能是甘薯耐旱育种计划的潜在候选基因。该分析提供了关于栽培甘薯的两个二倍体野生近缘种中NAC家族基因的全面系统信息，并将为其功能表征和利用提供蓝图，以提高甘薯对非生物胁迫的耐受性。
