He Xiaoyan, Zeng Jianbin, Cao Fangbin, Ahmed Imrul Mosaddek, Zhang Guoping, Vincze Eva, Wu Feibo
Department of Agronomy, College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, Hangzhou 310058, PR China.
Department of Molecular Biology and Genetics, University of Aarhus, Fosøgsvej 1, DK-4200 Slagelse, Denmark.
J Exp Bot. 2015 Dec;66(22):7405-19. doi: 10.1093/jxb/erv436. Epub 2015 Sep 28.
Tibetan wild barley is a treasure trove of useful genes for crop improvement including abiotic stress tolerance, like drought. Root hair of single-celled structures plays an important role in water and nutrition uptake. Polyethylene-glycol-induced drought stress hydroponic/petri-dish experiments were performed, where root hair morphology and transcriptional characteristics of two contrasting Tibetan wild barley genotypes (drought-tolerant XZ5 and drought-sensitive XZ54) and drought-tolerant cv. Tadmor were compared. Drought-induced root hair growth was only observed in XZ5. Thirty-six drought tolerance-associated genes were identified in XZ5, including 16 genes specifically highly expressed in XZ5 but not Tadmor under drought. The full length cDNA of a novel β-expansin gene (HvEXPB7), being the unique root hair development related gene in the identified genes, was cloned. The sequence comparison indicated that HvEXPB7 carried both DPBB_1 and Pollon_allerg_1 domains. HvEXPB7 is predominantly expressed in roots. Subcellular localization verified that HvEXPB7 is located in the plasma membrane. Barley stripe mosaic virus induced gene silencing (BSMV-VIGS) of HvEXPB7 led to severely suppressed root hairs both under control and drought conditions, and significantly reduced K uptake. These findings highlight and confer the significance of HvEXPB7 in root hair growth under drought stress in XZ5, and provide a novel insight into the genetic basis for drought tolerance in Tibetan wild barley.
青稞是作物改良的有用基因宝库，包括对非生物胁迫（如干旱）的耐受性。单细胞结构的根毛在水分和养分吸收中起重要作用。进行了聚乙二醇诱导的干旱胁迫水培/培养皿实验，比较了两种对比鲜明的青稞基因型（耐旱的XZ5和干旱敏感的XZ54）以及耐旱品种Tadmor的根毛形态和转录特征。仅在XZ5中观察到干旱诱导的根毛生长。在XZ5中鉴定出36个与耐旱相关的基因，其中16个基因在干旱条件下在XZ5中特异性高表达，而在Tadmor中不表达。克隆了一个新的β-扩张蛋白基因（HvEXPB7）的全长cDNA，它是鉴定出的基因中唯一与根毛发育相关的基因。序列比较表明，HvEXPB7具有DPBB_1和Pollon_allerg_1结构域。HvEXPB7主要在根中表达。亚细胞定位证实HvEXPB7位于质膜上。HvEXPB7的大麦条纹花叶病毒诱导基因沉默（BSMV-VIGS）导致在对照和干旱条件下根毛均受到严重抑制，钾吸收显著降低。这些发现突出并赋予了HvEXPB7在XZ5干旱胁迫下根毛生长中的重要性，并为青稞耐旱性的遗传基础提供了新的见解。
