水稻突变体D12W191多分蘖表型产生与细胞分裂素的关系

[目的] 本研究旨在比较水稻矮秆多分蘖突变体D12W191与野生型‘武育粳3号’的细胞分裂素（CTK）和生长素（IAA）含量差异以及相关基因表达情况，并探究分蘖生长抑制剂萘乙酸（NAA）处理对其分蘖芽形态发育的影响及生理机制。[方法] 以野生型粳稻‘武育粳3号’及利用甲基磺酸乙酯（EMS）诱导突变获得的矮秆多分蘖突变体（编号为D12W191）为供试材料，测定分蘖芽及分蘖节的细胞分裂素（CTK）和生长素（IAA）含量，并分析细胞分裂素合成、降解和响应调节子基因及生长素合成基因的表达差异。[结果] D12W191分蘖芽的玉米素（Z）和玉米素核苷（ZR）含量均高于‘武育粳3号’，在分蘖节中未出现显著差异；与细胞分裂素变化趋势不同，突变体材料D12W191分蘖芽中IAA含量和’武育粳3号’相比没有差异，而分蘖节中的IAA含量低于‘武育粳3号’。IAA与Z+ZR比值分析表明，突变体D12W191分蘖芽和分蘖节的IAA/（Z+ZR）值均低于‘武育粳3号’。与野生型相比，D12W191的分蘖芽和分蘖节中的细胞分裂素合成基因OsIPT4、OsIPT5、OsIPT7表达上调，细胞分裂素降解基因OsCKX4、OsCKX5、OsCKX9表达下调，细胞分裂素响应调节子基因OsRR6、OsRR7、OsRR11也呈现下调的趋势，而且细胞分裂素合成抑制剂Lovastatin能够完全抑制多分蘖突变体分蘖的发生。生长素合成基因OsYUCCA3、OsYUCCA4在突变体分蘖芽和分蘖节中的表达量与野生型相比无显著差异，而OsYUCCA6在突变体分蘖节中显著下调，在分蘖芽中的表达与野生型处于同一水平。水稻OsTB1基因负调控分蘖的发生，其在突变体分蘖芽中表达明显下调。外源NAA处理抑制了2个材料分蘖芽的生长，并且使OsIPTs基因表达下调，OsCKXs和OsTB1基因表达上调。[结论] D12W191突变体OsIPTs表达上调及OsCKXs表达下调使分蘖芽中内源CTK含量上升，而细胞分裂素信号转导途径负调控因子A型OsRRs基因表达量下降，又增强了细胞分裂素的作用，这些都有利分蘖的发生，外源喷施细胞分裂素合成抑制剂Lovastatin试验结果进一步表明，突变体的多分蘖表型可能是由于分蘖芽中较高的CTK引起的。NAA处理显著抑制了D12W191分蘖芽的生长，这与其对OsIPTs、OsCKXs和OsTB1基因的调控有关。
[Objectives] The aim of study was to compare the contents of different phytohormones and the expression of genes related with tillering of a dwarf-multi-tiller rice mutant and its wild-type,and also to investigate the effect of external NAA on morphological traits of tiller buds and its physiological mechanism. [Methods] A dwarf-multi-tiller rice mutant D12W191 which was induced by ethylmethane sulfonate and its wild-type ‘Wuyujing 3’ were used as materials. IAA(indoleacetic acid),Z(zeatin) and ZR(ribosylzeatin) levels in tiller buds and nodes were determined,and the expression of genes related with cytokinin synthesis,degradation,signaling and auxin synthesis was analyzed. [Results] The contents of Z and ZR in tiller buds of D12W191 were higher than ‘Wuyujing 3’,but no significant difference was determined in tiller nodes. Furthermore,the level of IAA in tiller nodes of D12W191 was lower than ‘Wuyujing 3’,but in tiller buds the level of IAA between ‘Wuyujing 3’ and D12W191 was at the same level. The expression of OsIPT4,OsIPT5 and OsIPT7 was up-regulated both in tiller buds and tiller nodes of D12W191,while OsCKX4,OsCKX5,OsCKX9,OsRR6,OsRR7 and OsRR11 were down-regulated. The change trends of IAA synthesis genes were different between tiller buds and tiller nodes of ‘Wuyujing 3’ and D12W191. In tiller buds and nodes of D12W191 the expression of OsYUCCA3 and OsYUCCA4 did not change significantly compared with ‘Wuyujing 3’,but the expression of OsYUCCA6 was lower than ‘Wuyujing 3’ in tille