Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Unidad de Hortofruticultura, Gobierno de Aragón, Avda. Montañana, Zaragoza, Spain.
Instituto Agroalimentario de Aragón-IA2 (CITA-Universidad de Zaragoza), Calle Miguel Servet, Zaragoza, Spain.
PLoS One. 2021 Oct 13;16(10):e0252001. doi: 10.1371/journal.pone.0252001. eCollection 2021.
Almond breeding programs aimed at selecting cultivars adapted to intensive orchards have recently focused on the optimization of tree architecture. This multifactorial trait is defined by numerous components controlled by processes such as hormonal responses, gravitropism and light perception. Gravitropism sensing is crucial to control the branch angle and therefore, the tree habit. A gene family, denominated IGT family after a shared conserved domain, has been described as involved in the regulation of branch angle in several species, including rice and Arabidopsis, and even in fruit trees like peach. Here we identified six members of this family in almond: LAZY1, LAZY2, TAC1, DRO1, DRO2, IGT-like. After analyzing their protein sequences in forty-one almond cultivars and wild species, little variability was found, pointing a high degree of conservation in this family. To our knowledge, this is the first effort to analyze the diversity of IGT family proteins in members of the same tree species. Gene expression was analyzed in fourteen cultivars of agronomical interest comprising diverse tree habit phenotypes. Only LAZY1, LAZY2 and TAC1 were expressed in almond shoot tips during the growing season. No relation could be established between the expression profile of these genes and the variability observed in the tree habit. However, some insight has been gained in how LAZY1 and LAZY2 are regulated, identifying the IPA1 almond homologues and other transcription factors involved in hormonal responses as regulators of their expression. Besides, we have found various polymorphisms that could not be discarded as involved in a potential polygenic origin of regulation of architectural phenotypes. Therefore, we have established that neither the expression nor the genetic polymorphism of IGT family genes are correlated to diversity of tree habit in currently commercialized almond cultivars, with other gene families contributing to the variability of these traits.
杏仁的培育计划旨在选择适应集约化果园的品种，最近的重点是优化树木结构。这个多因素的特征由许多受激素反应、向重力性和光感知等过程控制的组成部分定义。向重力性感知对于控制枝条角度从而控制树形至关重要。一个被称为 IGT 家族的基因家族，因其共享的保守结构域而得名，已被描述为参与包括水稻和拟南芥在内的几种物种的枝条角度调控，甚至在桃树等果树上也有作用。在这里，我们在杏仁中鉴定了这个家族的六个成员：LAZY1、LAZY2、TAC1、DRO1、DRO2 和 IGT-like。在分析了 41 个杏仁品种和野生种的蛋白质序列后，发现它们的变异性很小，表明这个家族具有高度的保守性。据我们所知，这是首次分析同一树种 IGT 家族蛋白多样性的努力。在 14 个具有农业重要性的品种中分析了基因表达，这些品种包含了不同的树形表型。只有 LAZY1、LAZY2 和 TAC1 在杏仁生长季节的芽尖中表达。这些基因的表达谱与观察到的树形变异性之间没有关系。然而，我们已经获得了关于 LAZY1 和 LAZY2 如何被调控的一些见解，确定了 IPA1 杏仁同源物和其他参与激素反应的转录因子是它们表达的调节剂。此外，我们还发现了各种不能排除与调控结构表型的潜在多基因起源有关的多态性。因此，我们已经确定，在目前商业化的杏仁品种中，IGT 家族基因的表达或遗传多态性与树形多样性没有相关性，其他基因家族对这些性状的变异性有贡献。
