Key Lab of Biodiversity and Biotechnology of Jiangsu Province, College of Life Sciences, Nanjing Normal University, Nanjing 210097, PR China.
J Plant Physiol. 2010 Mar 1;167(4):277-85. doi: 10.1016/j.jplph.2009.09.017. Epub 2009 Dec 9.
In plants, it is well established that chloroplast is one of the early targgeted organelles to breakdown during leaves senescing. Here we applied a newly developed super-high-yield hybrid rice (Oryza sativa) LiangYouPeiJiu (LYPJ) and its parents lines to investigate changes in ultrastructure of chloroplasts, fatty acid composition of thylakoid membrane lipids and chlorophyll (Chl) a fluorescence transient in natural senescing leaves. We found that at full expansion of flag leaves in three lines, chloroplasts often showed oblong shapes with a typical membrane system of stroma and grana thylakoids, whereas their shapes had been changed from oblong to spherical during senescence. Our data showed that the initiation of senescence displayed accumulation of starch and an increase in the number and size of plastoglobuli with the damaged thylakoid membranes; subsequently, swollen thylakoid membranes in stroma and in grana with a significant increase in MDA content, and disorganization of thylakoid membrane system with significant changes in fatty acid composition of thylakoid membrane lipids were developed. Compared with its parents, the newly developed hybrid rice LYPJ had the highest capacity of carbohydrate transport from leaves (sources) to ears (sink), marked with the lowest accumulation of starch grains in the leaf chloroplasts, and the slowest senescing rate of chloroplast in overall leaf senescence process. Chl a fluorescence transients of three kinds of flag leaves were analyzed by so-called JIP-test. The results of analysis suggest that these findings inculding a high inherited activity of antioxidant enzymes and high photosynthetate transport to pretect chloroplast structure in the hybrid rice LYPJ have close relations to its super-high yield.
在植物中，已经证实叶绿体是叶片衰老过程中最早分解的细胞器之一。在这里，我们应用一种新开发的超高产杂交水稻（Oryza sativa）两优培九（LYPJ）及其亲本系来研究叶绿体超微结构、类囊体膜脂脂肪酸组成和叶绿素（Chl）a 荧光瞬变的变化在自然衰老叶片中。我们发现，在三个系的旗叶完全展开时，叶绿体通常呈现出典型的基质和基粒类囊体膜系统的长形，而在衰老过程中，它们的形状已经从长形变为球形。我们的数据表明，衰老的开始表现为淀粉的积累和质体小球数量和大小的增加，以及类囊体膜的损伤；随后，基质和基粒中的类囊体膜肿胀，MDA 含量显著增加，类囊体膜系统的组织紊乱，类囊体膜脂脂肪酸组成发生显著变化。与亲本相比，新开发的杂交水稻 LYPJ 具有从叶片（源）向穗（库）运输碳水化合物的最高能力，其叶片叶绿体中淀粉粒积累最低，整个叶片衰老过程中叶绿体衰老速度最慢。对三种旗叶进行了所谓的 JIP 测试的 Chl a 荧光瞬变分析。分析结果表明，这些发现包括抗氧化酶的高遗传活性和高光合产物运输，以保护叶绿体结构在杂交水稻 LYPJ 中与它的超高产密切相关。
