遗传抑制开花在幼年和成年柑橘树之间存在差异。
Genetic inhibition of flowering differs between juvenile and adult Citrus trees.
机构信息
Instituto Agroforestal Mediterraneo, Universitat Politècnica de València, Camino de Vera s/n, CP, Valencia, Spain.
CEBAS-CSIC, Campus Universitario de Espinardo, CP Murcia, Spain.
出版信息
Ann Bot. 2019 Feb 15;123(3):483-490. doi: 10.1093/aob/mcy179.
BACKGROUND AND AIMS
In woody species, the juvenile period maintains the axillary meristems in a vegetative stage, unable to flower, for several years. However, in adult trees, some 1-year-old meristems flower whereas others remain vegetative to ensure a polycarpic growth habit. Both types of trees, therefore, have non-flowering meristems, and we hypothesize that the molecular mechanism regulating flower inhibition in juvenile trees is different from that in adult trees.
METHODS
In adult Citrus trees, the main endogenous factor inhibiting flower induction is the growing fruit. Thus, we studied the expression of the main flowering time, identity and patterning genes of trees with heavy fruit load (not-flowering adult trees) compared to that of 6-month-old trees (not-flowering juvenile trees). Adult trees without fruits (flowering trees) were used as a control. Second, we studied the expression of the same genes in the meristems of 6-month, and 1-, 3-, 5- and 7-year-old juvenile trees compared to 10-year-old flowering trees.
KEY RESULTS
The axillary meristems of juvenile trees are unable to transcribe flowering time and patterning genes during the period of induction, although they are able to transcribe the FLOWERING LOCUS T citrus orthologue (CiFT2) in leaves. By contrast, meristems of not-flowering adult trees are able to transcribe the flowering network genes but fail to achieve the transcription threshold required to flower, due to CiFT2 repression by the fruit. Juvenile meristems progressively achieve gene expression, with age-dependent differences from 6 months to 7 years, FD-like and CsLFY being the last genes to be expressed.
CONCLUSIONS
During the juvenile period the mechanism inhibiting flowering is determined in the immature bud, so that it progressively acquires flowering ability at the gene expression level of the flowering time programme, whereas in the adult tree it is determined in the leaf, where repression of CiFT2 gene expression occurs.
背景和目的
在木本植物中，幼年期的腋芽分生组织会处于营养生长阶段，几年内无法开花。然而，在成年树木中，一些 1 龄分生组织会开花，而另一些则保持营养生长状态，以确保多歧式生长习性。因此，这两种类型的树木都有不开花的分生组织，我们假设调节幼年期树木花抑制的分子机制与成年树木不同。
方法
在成年柑橘树中，主要的内源因子抑制花诱导是生长中的果实。因此，我们研究了重果负载（不开花成年树）与 6 月龄树（不开花幼树）相比，主要开花时间、身份和模式基因的表达。未结果实的成年树（开花树）作为对照。其次，我们研究了 6 月龄、1、3、5 和 7 龄幼树的分生组织与 10 龄开花树的相同基因的表达。
主要结果
幼树的腋芽分生组织在诱导期无法转录开花时间和模式基因，尽管它们能够在叶片中转录柑橘 FLOWERING LOCUS T 同源物（CiFT2）。相比之下，不开花成年树木的分生组织能够转录开花网络基因，但由于果实抑制 CiFT2，无法达到开花所需的转录阈值。幼树的分生组织逐渐实现基因表达，从 6 月龄到 7 岁，存在年龄依赖性差异，FD-like 和 CsLFY 是最后表达的基因。
结论
在幼年期，开花抑制的机制在未成熟芽中确定，因此它逐渐在开花时间程序的基因表达水平上获得开花能力，而在成年树中，它在叶片中确定，在叶片中发生 CiFT2 基因表达的抑制。
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