Chen Qinchang, Zhang Xiaodan, Fang Yaxue, Wang Baiyu, Xu Shaosi, Zhao Kai, Zhang Jisen, Fang Jingping
College of Life Sciences, Fujian Normal University, Fuzhou, China.
Center of Engineering Technology Research for Microalgae Germplasm Improvement of Fujian, Southern Institute of Oceanography, Fujian Normal University, Fuzhou, China.
Front Plant Sci. 2022 Mar 25;13:820439. doi: 10.3389/fpls.2022.820439. eCollection 2022.
Longan ( Lour.) is a productive fruit crop with high nutritional and medical value in tropical and subtropical regions. The gene family is one of the most widespread plant transcription factor (TF) families participating in the flowering regulation. However, little is known about the MYB TFs involved in the flowering process in longan and its regulatory network. In this study, a total of 119 genes were identified in the longan genome and were phylogenetically grouped into 28 subgroups. The groupings were supported by highly conserved gene structures and motif composition of genes in each subgroup. Collinearity analysis demonstrated that segmental replications played a more crucial role in the expansion of the gene family compared to tandem duplications, and all tandem/segmental duplication gene pairs have evolved under purifying selection. Interspecies synteny analysis among longan and five representative species implied the occurrence of gene duplication events was one of the reasons contributing to functional differentiation among species. RNA-seq data from various tissues showed genes displayed tissue-preferential expression patterns. The pathway of flower development was enriched with six genes. -acting element prediction revealed the putative functions of genes were related to the plant development, phytohormones, and environmental stresses. Notably, the orthologous counterparts between Arabidopsis and longan R2R3-MYB members tended to play conserved roles in the flowering regulation and stress responses. Transcriptome profiling on off-season flower induction (FI) by KClO indicated two up-regulated and four down-regulated genes involved in the response to KClO treatment compared with control groups. Additionally, qRT-PCR confirmed certain genes exhibited high expression in flowers/flower buds. Subcellular localization experiments revealed that three predicted flowering-associated MYB proteins were localized in the nucleus. Future functional studies on these potential candidate genes involved in the flowering development could further the understanding of the flowering regulation mechanism.
龙眼（Lour.）是热带和亚热带地区一种高产的水果作物，具有很高的营养和药用价值。该基因家族是参与开花调控的最广泛的植物转录因子（TF）家族之一。然而，关于参与龙眼开花过程的MYB转录因子及其调控网络，人们了解甚少。在本研究中，在龙眼基因组中总共鉴定出119个基因，并在系统发育上分为28个亚组。每个亚组中基因高度保守的基因结构和基序组成支持了这些分组。共线性分析表明，与串联重复相比，片段重复在该基因家族的扩展中起更关键的作用，并且所有串联/片段重复基因对都在纯化选择下进化。龙眼与五个代表性物种之间的种间共线性分析表明，基因重复事件的发生是导致物种间功能分化的原因之一。来自各种组织的RNA-seq数据表明这些基因呈现组织优先表达模式。花发育途径中有六个基因富集。顺式作用元件预测表明这些基因的推定功能与植物发育、植物激素和环境胁迫有关。值得注意的是，拟南芥和龙眼R2R3-MYB成员之间的直系同源对应物在开花调控和胁迫反应中倾向于发挥保守作用。用KClO进行的淡季花诱导（FI）的转录组分析表明，与对照组相比，有两个上调和四个下调的基因参与了对KClO处理的反应。此外，qRT-PCR证实某些基因在花/花芽中高表达。亚细胞定位实验表明，三种预测的与开花相关的MYB蛋白定位于细胞核中。对这些参与开花发育的潜在候选基因的未来功能研究可能会进一步加深对开花调控机制的理解。
