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

对水稻衰老叶片胞质谷氨酰胺合成酶（GS1; EC 6.3.1.2）蛋白含量、穗数和穗重相关的数量性状位点（QTL）进行了鉴定。利用分子标记辅助选择选育的近等基因品系C-22，在不同氮素水平的温室和水田条件下进行了栽培。在Koshihikari遗传背景下，C-22从2号染色体上的Kasalath染色体上替换了一小段（约50 cM）。C-22叶片中GS1蛋白含量比光光低12-37%，这与粳稻染色体正影响的QTL区域一致。在营养早期阶段，C-22在温室中分蘖活跃程度高于光光。在繁殖阶段，C-22的穗数和总穗重均显著高于光，特别是在低氮条件下。这些性状在水田试验中得到进一步证实。因此，在营养早期，卡萨拉斯染色体对分蘖发育有积极影响，增加了C-22成熟期的穗数和穗重。这些数据表明，目标QTL （Pnn1；穗号1）在水稻分蘖和穗发育中起重要作用。Pnn1在6.7 cM区域被划界，表明在第2腋发育分蘖形成（RDT；在第2腋发育分蘖形成的比率）是用替代系确定的。利用Kasalath染色体的不同替代系，该QTL区域先后被缩小到23kb。GS1的生理功能；使用GS1的敲除突变体对1进行了研究；该研究结果将发表在《植物杂志》上。此外，还报道了可能参与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.