水稻叶片早衰突变体ospls7的生理特性及其基因定位

Physiological characters and gene mapping of a precocious leaf senescence mutant ospls7 in rice(Oryza sativa L.)

衰老是叶片发育的最后阶段,但叶片,尤其是功能叶,早衰将影响作物的产量与品质,因此,研究叶片早衰的分子生理机制对培育耐早衰优良品种具有重要意义。通过60Co-γ辐射诱变旱稻Monolaya获得一个稳定遗传的叶片早衰突变体ospls7,本文对其形态、叶片衰老生理特征、茎节细胞特性以及衰老性状遗传与基因定位等方面进行了研究。大田条件下,突变体ospls7叶片早衰性状始于三至四叶期幼苗,主要表现为:叶尖及中上部叶边缘黄色褐化并最终枯萎,成熟期穗长和各茎节长度均极显著短于野生型对照,最终导致植株矮化。究其原因,可能是由于突变体茎节细胞变短。叶片衰老生理结果表明,与野生型对照相比,孕穗期突变体ospls7倒二叶和倒三叶的叶绿素总含量、净光合速率、可溶性蛋白、过氧化氢酶活性均极显著降低,致使其叶片中H2O2大量累积并引起丙二醛含量急剧增加。同时,孕穗期突变体ospls7剑叶、倒二叶和倒三叶的内源ABA含量均极显著高于野生型对照,qRT-PCR结果证实ABA大量累积的原因在于ABA合成基因OsNCED3和OsAAO3显著上调,而其代谢基因OsABA8ox2和OsABA8ox3则显著下调。遗传分析结果表明,突变体ospls7的叶片早衰性状受单隐性核基因调控,进一步利用图位克隆技术将该基因定位于10号染色体的InDel标记ID74-33/34和SSR标记RM25040之间,物理距离为207 kb,这些结果为最终克隆OsPLS7基因并研究其功能奠定了基础。

Leaf senescence is the final stage of leaf development,however,premature aging of leaves,especially functional leaves,leads to reduction of yield and quality.Thus,it is very important for developing novel crop germplasms with delayed leaf-senescence characteristics through investigating the molecular and physiological mechanism of leaf senescence.In this study,a stable precocious leaf senescence mutant ospls7 was obtained from 60Coγ-radiated upland rice cultivar Monolaya,and its mor-phology,physiological characteristics of leaf senescence,cytological observation of internodes,genetic analysis and gene mapping were investigated.Under field conditions,leaf senescence was noticed as early as the 3-4-leaf seedling stage,featuring yel-lowing and browning at the edge of tip and the upper middle parts of old leaves and finally wilting.Due to shorter length of the parenchyma cells,panicle length and all internodes length of ospls7 were significantly shorter compared with wild type plants at the mature stage,resulting in dwarf phenotype in ospls7.Physiological analysis of leaf senescence indicated that compared to the wild type plants,the total chlorophyll contents,net photosynthetic rate,soluble protein content,and catalase(CAT)activity of the second and third leaves from top in ospls7 were significantly declined at the booting stage,which in turn resulting in the accumu-lation of H2O2 and a steady increase of malondialdehyde(MDA)contents in the mutant leaves.Moreover,due to significant up-regulation of ABA biosynthetic genes(OsNCED3 and OsAAO3)and significant down-regulation of the ABA catabolism genes(OsABA8ox2 and OsABA8ox3),the endogenous ABA levels in the leaves of ospls7 were significantly higher compared with the wild type at the booting stage.Genetic analysis and gene mapping showed that ospls7 was controlled by a single recessive nuclear gene,located in a region of 207 kb between SSR marker RM25040 and the InDel marker ID74-33/34 of chromosome 10.These results would further facilitate the cloning and functional analysis of OsPLS7 gene.