Department of Biology and Geology, Agri-Food Campus of International Excellence (CeiA3) and Research Centre CIAMBITAL, University of Almería, Almería, Spain.
Department of Plant Physiology, University of Granada, Granada, Spain.
Physiol Plant. 2023 Jan;175(1):e13864. doi: 10.1111/ppl.13864.
The enhanced salt tolerance of squash ethylene-insensitive mutants during germination and early stages of seedling development suggested that abscisic acid (ABA) could mediate this tolerance. To gain insight into the crosstalk between ethylene and ABA in seed germination, the germination rate and early seedling growth of wild type (WT) and ethylene-insensitive etr2b mutant were compared in seeds germinated under water and exogenous ABA treatment. The etr2b seeds germinated earlier than WT under both water and ABA, and the effect of ABA on radicle length and seedling growth of etr2b was lower than in WT, indicating that etr2b is also insensitive to ABA. The comparison of ABA and ethylene contents and ABA and ethylene gene expression profiles in WT and etr2b dry and imbibed seeds in either water, NaCl or ABA demonstrated a clear crosstalk between ethylene and ABA in germination. The expression profiles of ethylene genes in WT and etr2b indicated that the role of ethylene in seed germination does not appear to follow the canonical ethylene signaling pathway. Instead, etr2b reduces ABA content during formation of the seeds (dry seeds) and in response to seed imbibition and germination, which means diminished dormancy in the ethylene mutant. The etr2b mutation downregulated the expression of ABA biosynthesis and signaling genes during germination, demonstrating the positive role of ethylene receptor gene CpETR2B on seed germination and early seedling growth in squash is mediated by ABA. The reduced effect of exogenous ABA on ethylene production and ethylene gene expression in etr2b seeds suggests that this regulation is also dependent on ethylene.
在萌发和幼苗早期发育过程中，南瓜乙烯不敏感突变体的耐盐性增强，这表明脱落酸（ABA）可以介导这种耐受性。为了深入了解乙烯和 ABA 在种子萌发过程中的串扰，比较了在水和外源 ABA 处理下发芽的野生型（WT）和乙烯不敏感 etr2b 突变体种子的发芽率和早期幼苗生长。在水和 ABA 条件下，etr2b 种子的萌发均早于 WT，ABA 对 etr2b 根长和幼苗生长的影响低于 WT，表明 etr2b 也对 ABA 不敏感。ABA 和乙烯含量以及 WT 和 etr2b 干种子和吸胀种子在水、NaCl 或 ABA 中的 ABA 和乙烯基因表达谱的比较表明，ABA 和乙烯在萌发过程中存在明显的串扰。WT 和 etr2b 中乙烯基因的表达谱表明，乙烯在种子萌发中的作用似乎并不遵循典型的乙烯信号通路。相反，etr2b 在种子形成过程中（干种子）以及种子吸胀和萌发时降低 ABA 含量，这意味着乙烯突变体的休眠减弱。etr2b 突变下调了萌发过程中 ABA 生物合成和信号基因的表达，表明乙烯受体基因 CpETR2B 在南瓜种子萌发和早期幼苗生长中的积极作用是通过 ABA 介导的。外源 ABA 对 etr2b 种子中乙烯生成和乙烯基因表达的影响降低表明，这种调节也依赖于乙烯。
