水稻矮化宽叶突变体osdwl1的生理特性和基因定位

株高是影响水稻倒伏的重要因素之一,培育适度矮化水稻品种有利于提高其抗倒性,进而减少产量损失并提高稻米品质,因此研究矮秆形成的分子生理机制具有重要意义。通过辐射诱变籼稻恢复系自选1号获得一个稳定遗传的矮化宽叶突变体osdwl1,本文对其形态与生理特征、细胞结构差异、遗传分析和基因定位等方面进行了研究。大田条件下,osdwl1矮化宽叶性状始于分蘖期后,成熟期穗长和各茎节长度均极显著短于对照,最终导致株高矮化,究其原因,是由于突变体茎节细胞变短所致;而叶片石蜡切片及扫描电镜结果显示,osdwl1的叶片小维管束数及其间距显著增加,从而导致叶片变宽,且其上下表皮的小刺毛数也极显著增加。此外,osdwl1的中上部叶片还表现黄化症状,该性状始于3~4叶期幼苗。生理分析和透射电镜观察表明,与野生型对照相比,孕穗期osdwl1的叶绿体类囊体结构松散,且部分已开始降解,从而导致其倒二叶和倒三叶的叶绿素总含量、净光合速率以及Fv/Fm比值均极显著降低,而其可溶性蛋白、过氧化氢酶及超氧化物歧化酶酶活依次极显著降低,从而导致叶中H2O2及O2-累积,促使丙二醛含量急剧增加。遗传分析表明,osdwl1的矮化宽叶表型受单隐性核基因调控,利用图位克隆技术将该基因定位于6号染色体短臂的SSR标记RM19297与InDel标记ID269-2之间,物理距离为333kb,该结果为进一步克隆OsDWL1基因并研究其功能奠定了基础。

Physiological characters and gene mapping of a dwarf and wide-leaf mutant osdwl1 in rice(Oryza sativa L.)

Plant height is one of the important factors affecting rice lodging.The semi-dwarf rice varieties possess high level of lodging resistance,and could reduce yield loss and improve grain quality.Thus,it is very important to study the molecular and physiological mechanism of dwarf formation in rice.In this study,a stable hereditary dwarf and wider-leaf mutant osdwl1 was obtained from 60Coγ-radiated indica restore line Zixuan 1,and its morphological and physiological characteristics,cytological observation,genetic analysis and gene mapping were investigated.Under field condition,the mutant osdwl1 exhibited dwarf and wider-leaf after the tillering stage due to shorter length of the parenchyma cells,and its panicle length and all internodes length were significantly shorter compared with wild type plants at mature stage.Paraffin sections and scanning electronic microscopy(SEM)observation revealed that the number of small vascular(SV)bundles and the distance between SVs increased significantly,resulting in wider-leaf blade in osdwl1.Moreover,the number of microhairs on the abaxial and adaxial epidermis were also increased significantly in osdwl1.In addition,starting at the 3–4 leaf seedling stage,yellowing was visible at the upper middle parts of old leaves in osdwl1.Physiological analysis and transmission electron microscopy(TEM)observation indicated that the lamellar structure of chloroplast was distorted and began to collapse in some mesophyll cells,which led to the reduction of total chlorophyll contents,net photosynthetic rate and Fv/Fm ratio of the second and third leaves from top in osdwl1 at the heading stage.Relative to the wild type plants,the soluble protein content,catalase(CAT)and superoxide dismutase(SOD)activities were significantly decreased,which in turn resulting in the accumulation of H2O2 and O2-,and a steady increase of malondialdehyde(MDA)contents in the mutant leaves.Genetic analysis and gene mapping showed that osdwl1 was controlled by a single recessive nuclear gene,located in a region of 333 kb between SSR marker RM19297 and the In Del marker ID269-2 on the short arm of chromosome 6.The results would further facilitate the cloning and functional analysis of OsDWL1 gene.