Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE, Buenos Aires, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CP1428, Buenos Aires, Argentina.
Sci Rep. 2021 May 6;11(1):9688. doi: 10.1038/s41598-021-88874-5.
The germination timing of seeds is of the utmost adaptive importance for plant populations. Light is one of the best characterized factors promoting seed germination in several species. The germination is also finely regulated by changes in hormones levels, mainly those of gibberellin (GA) and abscisic acid (ABA). Here, we performed physiological, pharmacological, and molecular analyses to uncover the role of ATHB2, an HD-ZIP II transcription factor, in germination of Arabidopsis seeds. Our study demonstrated that ATHB2 is a negative regulator and sustains the expression of transcription factors to block germination promoted by light. Besides, we found that ATHB2 increases ABA sensitivity. Moreover, ABA and auxin content in athb2-2 mutant is higher than wild-type in dry seeds, but the differences disappeared during the imbibition in darkness and the first hours of exposition to light, respectively. Some ABA and light transcription factors are up-regulated by ATHB2, such as ABI5, ABI3, XERICO, SOMNUS and PIL5/PIF1. In opposition, PIN7, an auxin transport, is down-regulated. The role of ATHB2 as a repressor of germination induced by light affecting the gemination timing, could have differential effects on the establishment of seedlings altering the competitiveness between crops and weeds in the field.
种子的萌发时机对植物种群具有至关重要的适应意义。光是促进多种物种种子萌发的最佳特征因素之一。激素水平的变化，主要是赤霉素（GA）和脱落酸（ABA）的变化，也对萌发进行精细调节。在这里，我们进行了生理、药理学和分子分析，以揭示 HD-ZIP II 转录因子 ATHB2 在拟南芥种子萌发中的作用。我们的研究表明，ATHB2 是一个负调控因子，维持转录因子的表达以阻止光促进的萌发。此外，我们发现 ATHB2 增加了 ABA 的敏感性。此外，athb2-2 突变体在干种子中的 ABA 和生长素含量高于野生型，但在黑暗中吸胀和暴露于光的最初几个小时，差异分别消失。一些 ABA 和光转录因子被 ATHB2 上调，如 ABI5、ABI3、XERICO、SOMNUS 和 PIL5/PIF1。相反，生长素运输 PIN7 被下调。ATHB2 作为光诱导萌发的抑制剂的作用，可能通过影响萌发时机，对田间作物和杂草之间的竞争力产生差异效应，从而改变幼苗的建立。
