中文摘要：

LFY（LEAFY）及其同源基因是控制高等植物从营养生长向生殖生长转变的重要基因，对这些基因进行深入研究具有缩短林木幼龄期和改良花卉花期的实际应用价值。为了深入研究LFY氨基酸序列变化对其功能的影响，本研究以lfy2和lfy5为材料分析了这2个突变体表型变异及突变位点的特点。表型观察表明：虽然Ify2和Ify5属于不同的生态型，但是表型变异类似；try突变体花期比野生型推迟14d，茎生叶和次生枝的数目增多，花器官缺失并且被同源异型化。序列分析发现：lfy2的LFY氨基酸序列中只发生了P236L位点变异，Ify5的LFY氨基酸序列中发生变异的位点为F42L、V209A和P236L，其中F42L和V209A是非保守位点变异。Q—PCR结果显示：lfy2的花序中TFLI和FLC表达上调，Fr和AP2表达下降，APl、AP3、AG几乎没有表达。这些结果表明，由于LFY—C端结构域内236位氨基酸发生突变引起LFY功能缺失，导致了lfy2和lfy5表型变异。

英文摘要：

LFY and its homologs are key integrators controlling the vegetative-to-reproductive transition in higher plants. A better understanding of flowering-time genes possesses practical applications for shortening tree juvenility and improving flower bloom period. To examine the effects of amino acid sequence changes of LFY on its function in Arabidopsis, the phenotypic variation and sequence characterization of Ify2 and Ify5 were investigated in this study. The results showed that although Ify2 and lfy5 derived from different ecotypes of Arabidopsis, the phenotypic variations of mutants were similar. The flowering time of/fy mutants was 14 days later than wild-type,the numbers of cauline leaves and lateral shoots were increased, and the floral organs were missing and homeotic. Sequence analysis revealed that the amino acid mutation sites of LFY were P236L in lfy2, and F42L, V209A and P236L in lfy5 with F42L and V209A being at non-conserved sites. Q-PCR analysis showed that the transcript levels of FLC and TFL1 were increased in the inflorescence of lfy, and those of FT and AP2 were decreased, while AP1, AP3 and AG were not expressed. These results suggest that mutation at the site of 236 on LFY-C domain caused the loss of LFY function and was responsible for the mutant phenotype in lfy2 and lfy5.