水稻早衰叶突变体PLS2的遗传分析与基因定位

叶片早衰引起叶绿素和其他大分子被降解,叶片光合能力降低。这个过程常伴随着活性氧(ROS)的积累,以及细胞中抗氧化酶(SOD、CAT和APX)活性的降低,衰老相关基因(SAG)表达量上调,最终导致整个植株过早成熟,产量降低。因此,研究水稻早衰遗传机制和基因功能对于水稻的遗传改良具有重要的作用和意义。PLS2是通过航天育种工程经空间辐射诱变得来的突变体,在孕穗期表现早衰。与野生型相比,PLS2的光合能力降低,株高变矮,节间和穗长缩短,分蘖数和有效分蘖数减少,穗粒数和结实率明显下降,千粒重降低,穗发育不良,灌浆不充分;叶片的CAT活性显著降低、H2O2积累、死亡细胞增加,叶绿体结构变差,叶绿体中淀粉和嗜锇颗粒增多。黑暗处理加速突变体叶片衰老,叶绿体超微结构球状化。利用PLS2/蜀恢527和PLS2/02428的隐性定位群体,将pls2定位在第3染色体标记RM14704(8 674 283 bp)与SL-I-5(8 758 394 bp)之间,物理距离84.11 kb,区间内包括14个基因,测序发现在LOC_Os03g15840第9个外显子第41位的C被替换为T,导致精氨酸(R)替换为半胱氨酸(C),LOC_Os3g15840编码水稻中的一个糖基转移酶(glycosyltransferases,GTs),可能是pls2的候选基因。为下一步调控基因的克隆和功能研究奠定了基础。

Genetic Analysis and Fine Mapping of a Premature Leaf Senescence Mutant in Rice (Orzya sativa L.)

Leaf senescence induces degradation of chlorophyll and other macromolecules, reducing leaf photosynthetic capacity. This process is accompanied by the accumulation of reactive oxygen species (ROS), the decreasing of cell antioxidant enzyme (SOD, CAT, and APX) activity, and the increasing of aging related gene (SAG) expression, leading in early maturity and yield reduction. Therefore, studies on the genetic mechanism and gene function of premature senescence in rice, has the important effect and significance.in genetic improvement of rice. PLS2 from space radiation mutation breeding project showed leaf senility, at booting stage. Compared with the wild type, in PLS2 the photosynthetic capacity decreased, the plant height, internode and panicle length shortened, tiller and effective tiller number reduced, number of grains per ear and seed setting rate were significantly lower, 1000-grain weight decreased, main panicle was stunted and grain-filling was not full. CAT activity decreased significantly in leaves, H₂O₂ accumulated, and the number of dead cell increased, chloroplast structures in leaves were worse, with more starches grains and osmiophilic granules. Dark treatment accelerated mutant leaf senescence, chloroplast ultrastructure was spheroidized. Using implicit localization population derived from PLS2/Shuhui 527 and PLS2/02428 the pls2 was located between markers RM14704 (8 674 283 bp) and SL-I-5 (8 758 394 bp) on chromosome 3, with physical distance of 84.11 kb, including 14 genes in the interval. Sequencing result showed that C was replaced by T in the position of 41 base pair of the ninth extron of LOC_Os03g15840 leading to an exchange of Arg (R) is replaced by Cys(C). LOC_Os03g15840 coding a glycosyl transferase (GTs) may be the candidate gene of pls2. These results provide a foundation for the further gene cloning and functional analysis of pls2.