Nitrogen Recycling System Analyzed by Molecular Physiology together with QTL Analysis in Rice

在水稻（Oryza sativa L.）中定位了一个与衰老叶片胞质谷氨酰胺合成酶（GS 1; EC 6.3.1.2）蛋白质含量、穗数和穗重相关的数量性状位点（QTL）。通过分子标记辅助选择培育的近等基因系C-22在不同氮素水平下进行了温室和大田试验。C-22有一个小片段（约50 cM）取代Kasalath染色体2号染色体上的越光遗传背景。C-22的叶片中GS 1蛋白含量比越光低12-37%，这与一个受粳稻染色体正影响的QTL区域一致。在营养生长早期，C-22比越光在温室中具有更多的活跃分蘖。在生殖生长期，C-22的穗数和总穗重均显著高于越光，特别是在低氮条件下。C-22的这些性状在稻田中得到了进一步的证实。因此，Kasalath染色体在营养生长早期对分蘖的发育有积极影响，在C-22成熟期增加了穗数和穗重。这些数据表明目标QTL（Pnn 1;穗数1）在水稻分蘖和穗的发育中是重要的。Pnn 1被划定在6.7厘米的区域，表明在第二腋（RDT ;在第二腋的发展中的分蘖形成的比率）确定使用替代线。利用Kasalath染色体的不同替代系将该QTL区域缩小到23 kb，并利用GS 1; 1基因的敲除突变体研究了GS 1; 1的生理功能，该结果将发表在《植物杂志》上。此外，还发表了预期参与Gln信号传导的PII样蛋白的功能。

A quantitative trait locus (QTL) associated with the protein content of cytosolic glutamine synthetase (GS1 ; EC 6.3.1.2) in senescing leaves, panicle number and panicle weight was characterized in rice (Oryza sativa L.). A nearly isogenic line (NIL), C-22, developed by marker-assisted selection was grown under different nitrogen levels in a greenhouse and in a paddy field. C-22 had a small segment (approximately 50 cM) substituted from the Kasalath chromosome in chromosome 2 on a Koshihikari genetic background. C-22 showed a 12-37% lower content of GS1 protein in leaf blades than Koshihikari, which was in good agreement with a QTL region positively affected by the japonica chromosome. At an early vegetative stage, C-22 had more active tillers than Koshihikari in the greenhouse. At the reproductive stage, both panicle number and total panicle weight of C-22 were significantly higher than those of Koshihikari, particularly when grown with a low-nitrogen condition. These traits of C-22 were further confirmed in a paddy field. Thus, development of tillers was positively affected by the Kasalath chromosome at an early vegetative stage, which increased the panicle number and panicle weight at the mature stage in C-22. These data indicate that the target QTL (Pnn1 ; panicle number 1) is important in the development of tillers and panicles in rice. Pnn1 was delimited at the 6.7 cM region, demonstrating that developing tiller formation in the 2nd axil (RDT ; ratio of developing tillers formation in the 2nd axil) was determined using substituted lines. This QTL region has been successively narrowed down to 23 kb using various substituted lines of Kasalath chromosome.Physiological function of GS1 ; 1 has been investigated using knock-out mutants of GS1 ; 1 gene and this result will be published in Plant Journal. In addition, function of PII-like protein that would be expected to be involved in the Gln signaling has also been published.