Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de Valencia, 46022 Valencia, Spain.
Departament de química inorgànica i orgànica, Universitat Jaume I, 12071 Castelló, Spain.
Plant Physiol. 2024 Jul 31;195(4):2743-2756. doi: 10.1093/plphys/kiae234.
Flowers, and hence, fruits and seeds, are produced by the activity of the inflorescence meristem after the floral transition. In plants with indeterminate inflorescences, the final number of flowers produced by the inflorescence meristem is determined by the length of the flowering period, which ends with inflorescence arrest. Inflorescence arrest depends on many different factors, such as the presence of seeds, the influence of the environment, or endogenous factors such as phytohormone levels and age, which modulate inflorescence meristem activity. The FRUITFULL-APETALA2 (FUL-AP2) pathway plays a major role in regulating the end of flowering, likely integrating both endogenous cues and those related to seed formation. Among AP2 targets, HOMEOBOX PROTEIN21 (HB21) has been identified as a putative mediator of AP2 function in the control of inflorescence arrest. HB21 is a homeodomain leucine zipper transcription factor involved in establishing axillary bud dormancy. Here, we characterized the role of HB21 in the control of the inflorescence arrest at the end of flowering in Arabidopsis (Arabidopsis thaliana). HB21, together with HB40 and HB53, are upregulated in the inflorescence apex at the end of flowering, promoting floral bud arrest. We also show that abscisic acid (ABA) accumulation occurs in the inflorescence apex in an HB-dependent manner. Our work suggests a physiological role of ABA in floral bud arrest at the end of flowering, pointing to ABA as a regulator of inflorescence arrest downstream of the HB21/40/53 genes.
花，以及由此产生的果实和种子，是在花转变后由花序分生组织的活动产生的。在具有不定花序的植物中，花序分生组织产生的最终花数由开花期的长度决定，开花期的结束伴随着花序的停止。花序的停止取决于许多不同的因素，例如种子的存在、环境的影响或内源性因素，如植物激素水平和年龄，这些因素调节花序分生组织的活性。FRUITFULL-APETALA2（FUL-AP2）途径在调节开花结束中起着重要作用，可能整合了内源性线索和与种子形成有关的线索。在 AP2 靶标中，同源盒蛋白 21（HB21）已被确定为 AP2 功能在控制花序停止中的一个假定介质。HB21 是一个同源盒亮氨酸拉链转录因子，参与建立腋芽休眠。在这里，我们研究了 HB21 在拟南芥（Arabidopsis thaliana）开花结束时控制花序停止中的作用。HB21 与 HB40 和 HB53 一起在开花结束时的花序顶端上调，促进花芽停止。我们还表明，脱落酸（ABA）以 HB 依赖的方式在花序顶端积累。我们的工作表明 ABA 在开花结束时花芽停止中的生理作用，指出 ABA 是 HB21/40/53 基因下游花序停止的调节剂。
