Li Qiaoxia, Zhu Yuanyuan, Li Youlong, Chen Chenlong, Li Jigang, Sun Kun, He Chaoying
Life Science College, Northwest Normal University, Anning East Road 967, Anning, Lanzhou, Gansu, 730070, China.
State Key Laboratory of Plant Diversity and Specialty Crops / State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing, 100093, China.
BMC Plant Biol. 2025 Mar 12;25(1):319. doi: 10.1186/s12870-025-06348-6.
Viola philippica and V. prionantha develop chasmogamous (CH) flowers under ≤ 12-h daylight conditions and cleistogamous (CL) flowers under long daylight (> 12-h daylight) conditions (LD), whereas V. cornuta develops CH flowers regardless of the daylight conditions. APETALA3 (AP3) is a major floral B-function gene that regulates the organ identity and development of stamens and petals. Evolutionary changes in AP3 orthologous genes might involve in the dimorphic flower formation. In the present study, we compared AP3 orthologous genes among three Viola species.
The AP3 sequences were highly conserved, and obligate AP3-PISTILLATA heterodimers were universally formed. However, the floral expression of VphAP3 in V. philippica and VprAP3 in V. prionantha changed in response to the photoperiod. Their expression was significantly higher under 12-h daylight conditions than under 16-h daylight conditions. In contrast, VcoAP3 expression in the floral buds of V. cornuta was comparable among photoperiods. In accordance with these variations in expression, correlated sequence divergences were observed in the putative regulatory regions of Viola AP3 orthologous genes.
Developmental inhibition of petals and stamens may result from AP3 downregulation by LD, which thereby induces CL flowers. Our study provides insight into the molecular basis underlying the developmental evolution of environmentally dependent mating systems in dimorphic CL plants.
在日照时长≤12小时的条件下，紫花地丁和早开堇菜会发育出完全花（CH），而在长日照（日照时长>12小时）条件下则发育出闭花受精花（CL）；相反，角堇无论在何种日照条件下均发育完全花。APETALA3（AP3）是一个主要的花B功能基因，可调控雄蕊和花瓣的器官特性及发育。AP3直系同源基因的进化变化可能与二型花的形成有关。在本研究中，我们比较了三种堇菜属植物的AP3直系同源基因。
AP3序列高度保守，且普遍形成AP3 - PISTILLATA异源二聚体。然而，紫花地丁中的VphAP3和早开堇菜中的VprAP3的花表达会随着光周期而变化。它们在12小时日照条件下的表达显著高于16小时日照条件下的表达。相比之下，角堇花芽中的VcoAP3表达在不同光周期下相当。根据这些表达变化，在堇菜属AP3直系同源基因的假定调控区域观察到相关的序列差异。
长日照导致AP3表达下调，进而可能抑制花瓣和雄蕊的发育，从而诱导闭花受精花的形成。我们的研究为二型闭花受精植物中环境依赖性交配系统发育进化的分子基础提供了见解。
