分蘖相关基因在再生稻腋芽萌发期的表达分析

【目的】明确分蘖相关基因在再生稻腋芽萌发期的表达动态变化，为阐明水稻再生季腋芽发育的调控机理提供理论依据。【方法】以再生分蘖能力强的材料i21和再生分蘖能力弱的材料i89为研究对象，运用实时荧光定量PCR（qRT-PCR）检测8个分蘖相关基因在水稻头季（分蘖始期和拔节孕穗期）和再生季不同时期（头季去穗后1、24、48和72 h）的表达动态变化，并分析分蘖相关基因间及其与最大再生分蘖的相关性，筛选出与腋芽生长相关性高的基因。【结果】自头季稻稻穗收割后，材料i21和i89的再生分蘖数的变化趋势基本一致，均随着腋芽的生长再生分蘖数逐渐增多，收割后20 d达最多并趋于稳定，但材料i21再生季发苗多且快，再生分蘖发生速度明显高于材料i89；材料i21和i89的最大再生分蘖数为33和10个。LAX1、LAX2和MOC1基因的相对表达量在不同材料不同时期间均存在明显差异，其中自头季去穗后，除MOC1基因在头季去穗后72 h的相对表达量外，LAX1、LAX2和MOC1基因在水稻再生分蘖形成期均表现为材料i21中的相对表达量极显著高于材料i89（P<0.01，下同），MOC1基因在头季去穗后1 h达峰值，LAX1和LAX2基因在头季去穗后24 h达峰值，随后显著降低（P<0.05，下同）并趋于稳定。头季去穗后，除TAD1基因在头季去穗后24 h时外，材料i89中D10、HTD1、OsTB1和TAD1基因的相对表达量均极显著高于材料i21中的相对表达量，D10和HTD1基因在头季去穗后1 h达峰值，OsTB1和TAD1基因在头季去穗后24和48 h达峰值，D27基因在材料i21和i89中的相对表达量均先升高后降低，且头季去穗后24~72 h，D27基因在材料i21中的表达量极显著高于材料i89。最大再生分蘖数分别与LAX2和MOC1基因的表达水平呈极显著和显著正相关，与D10、HTD1、OsTB1和TAD1基因的表达量呈极显著负相关。此外，不同基因的表达水平也存在不同相关性。【结论】LAX1、LAX2和MOC1基因高表达有利于水稻再生季分蘖的形成，D10、HTD1、OsTB1和TAD1基因高表达会抑制水稻再生季分蘖的形成。不同分蘖相关基因间存在相互作用，共同调控水稻再生季分蘖的形成。

Expression analysis of tiller-related genes during axillary bud outgrowth in ratoon rice

【Objective】The expression of tiller-related genes during axillary bud outgrowth in ratoon rice were profiled to provide insight into the molecular mechanisms underlying axillary bud development in the ratoon season.【Method】The rice varieties i21 and i89 with high and low ratooning abilities, respectively, were used as the study materials. Real-time fluorescence quantitatire PCR(qRFRCR) was used to characterize the expression dynamics of eight tiller-related genes at the stages of tiller initiation, elongation and booting of the first season and at 1, 24, 48 and 72 h after heading removal in the ratoon season. The correlation between tiller-related genes and maximum ratoon tillers was analyzed and the genes with high correlation with axillary bud growth were selected.【Result】The number of ratoon tillers in i21 and i89 increased gradually with the growth of axillary buds and reached a stable maximum 20 d after the first-season harvest. However, i21 ratoon tillers grew much faster than those of i89 and the maximum number of ratoon tillers of i21 and i89 were 33 and 10, respectively. The relative expression levels of LAX1, LAX2 and MOC1 genes differed significantly in the two varieties. The relative expression levels of LAX1, LAX2 and MOC1 genes in i21 were significantly higher than those in i89 during the ratooning period(P < 0.01, the same below). MOC1 reached peak levels at 1 h after beheading, whereas the expressions of LAX1 and LAX2 peaked at 24 h after beheading then decreased significantly(P < 0.05, the same below) to stable levels thereafter. During ratooning, the relative expression levels of D10, HTD1, OsTB1 and TAD1 genes in i89 were significantly higher than those in i21, except for TAD1 at 24 h after beheading. D10 and HTD1 genes peaked at 1 h after beheading, while OsTB1 and TAD1 genes reached their peak values later at 24 and 48 h after beheading. The relative expression levels of D27 in i21 and i89 increased initially but decreased at 24-72 h after heading removal, although this decrease in i21 was significantly less than that in i89. The maximum tiller number was positively and significantly correlated with the expression levels of LAX2 and MOC1 and negatively correlated with those of D10, HTD1, OsTB1 and TAD1. In addition, different gene expression levels also had different correlations.【Conclusion】The high expression of LAX1, LAX2 and MOC1 genes was beneficial to the formation of ratoon tillers, while the high expression of D10, HTD1, OsTB1 and TAD1 genes inhibited ratoon till outgrowth. This work indicates that the different tiller-related genes interacted to jointly regulate ratoon tiller formation.