A study on a mechanism of tipburn incidence and selection of resistant cultivars in lettuce

生菜(Lactuca sativa L.)烧伤是一种由缺钙引起的生理性疾病，会降低作物的价值。在本研究中，建立了一种有效的生菜对尖烧抗性的体外鉴定方法。用该方法鉴定出的一个敏感品种，验证了其作为环境监测指示植物的实用性。另一方面，从生菜(LsCAX2、3a、3b和5)中分离到4个与阳离子/H^+(CAX)交换相应的基因，以确定其与斑点病发生的相关基因。序列比对表明，参与钙选择的A和B结构域在两个LSCAX中都是保守的。CaCl2诱导的LsCAX基因在感病品种和抗病品种中的表达差异表明，这些基因可能与水稻青枯病的发生有关。ATDREB1A被认为是另一个负责的基因。AtDREB1A基因在生菜中的过表达增加了生菜叶尖烧焦的程度。这一结果表明，生菜尖烧的发生与胁迫反应有关。

Lettuce(Lactuca sativa L.) tipburn is a physiological disorder caused by calcium deficiency that decreases the crop value. In this study, an efficient method was established to evaluate lettuce resistance to tipburn in vitro. A sensitive cultivar identified by this method was validated its utility as indicator plants to monitor environmental conditions. On the other hand, to identify the responsible gene for tipburn incidence, four cDNAs corresponding to cation/H^+(CAX) exchanger were isolated from lettuce(LsCAX2, 3a, 3b, and 5). Sequence alignment revealed that both A and B domains which involved in calcium selection were conserved in two LSCAXs. The different expression of LsCAX genes by CaCl_2 between sensitive and resistant cultivars suggested the relevance of these genes to tipburn incidence. AtDREB1A was supposed to be another responsible gene. Overexpression of AtDREB1A in lettuce resulted in increasing tip-burned leaves. This result indicated that tipburn incidence is involved in stress response of lettuce.