Roles and evolution of four LEAFY homologs in floral patterning and leaf development in woodland strawberry

背景回顾：The plant-specific transcription factor LEAFY (LFY), generally maintained as a single copy gene in most angiosperm species, plays critical roles in flower development. The woodland strawberry (Fragaria vesca) possesses four LFY homologs in the genome; however, their respective functions and evolution remain unknown.

结果1-FveLFYa/b/c/d的功能：Here, we identified and validated that mutations in one of the four LFY homologs, FveLFYa, cause homeotic conversion of floral organs and reiterative outgrowth of ectopic flowers. In contrast to FveLFYa, FveLFYb/c/d appear dispensable under normal growth conditions, as fvelfyc mutants are indistinguishable from wild type and FveLFYb and FveLFYd are barely expressed. 

结果2-草莓和拟南芥LFY功能保守性：Transgenic analysis and yeast one-hybrid assay showed that FveLFYa and FveLFYb, but not FveLFYc and FveLFYd, are functionally conserved with AtLFY in Arabidopsis (Arabidopsis thaliana). 

结果3-FveLFY结合位点：Unexpectedly, LFY binding site prediction and yeast one-hybrid assay revealed that the transcriptional links between LFY and the APETALA1 (AP1) promoter/the large AGAMOUS (AG) intron are missing in F. vesca, which is due to the loss of LFY binding sites. The data indicate that mutations in cis-regulatory elements could contribute to LFY evolution. 

结果4-FevLFYa参与叶发育：Moreover, we showed that FveLFYa is involved in leaf development, as approximately 30% of mature leaves have smaller or fewer leaflets in fvelfya. 

结果5-草莓属LFY基因演化：Phylogenetic analysis indicated that LFY homologs in Fragaria species may arise from recent duplication events in their common ancestor and are undergoing convergent gene loss. 

结论：Together, these results provide insight into the role of LFY in flower and leaf development in strawberry and have important implications for the evolution of LFY.

在花发育中发挥重要作用的植物特异性转录因子LEAFY，在大多数的被子植物物种中均保持为单拷贝基因。野草莓（Fragaria vesca）基因组中编码了4个LFY同源基因，但是其各自的功能及演化仍不清楚。本文中，作者发现其中一个LFY基因FveLFYa突变会导致花器官的同源异型转化以及异位花的反复生长。与FveLFYa基因相反，正常条件下FveLFYb/c/d基因并非必需，具体表现为fvelfyc突变体与野生型相差无几且FveLFYb和FveLFYd几乎不表达。遗传转化和酵母单杂试验表明FveLFYa和FveLFYb与拟南芥的AtLFY基因功能保守，但是FveLFYc和FveLFYd基因不是。出乎意料地，LFY结合位点预测和酵母单杂试验表明，野草莓中AP1启动子和AG基因大段内含子中并不包含LFY的结合位点，因此他们之间不存在转录调控关联。这些数据表明，顺式调控元件的突变能够作用于LFY的演化。此外，作者还发现FveLFYa参与了叶片的发育，在fvelfya突变体中大约有30%的成熟叶片更小或者小叶更少。系统发育分析显示，草莓属物种中LFY同源基因可能起源于其共同祖先在近期发生的复制事件，并且经历了趋同性的丢失。综上，本文的研究结果揭示了草莓LFY基因在花和叶发育中的功能，并且对于LFY基因的演化提供了新的视野。

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