Graduate School of Science and Engineering, Saitama University, Japan.
J Plant Physiol. 2012 Jan 15;169(2):137-45. doi: 10.1016/j.jplph.2011.08.004. Epub 2011 Sep 28.
Overwintering plants develop tolerance to freezing stress through a cold acclimation process by which the cells provoke internal protective mechanisms against freezing. The stress hormone abscisic acid (ABA) is known to increase freezing tolerance of plant cells, but its role in cold acclimation has not been determined. In this study, we used ABA-insensitive lines of the moss Physcomitrella patens to determine whether cold acclimation in bryophytes involves an ABA-dependent process. Two ABA-insensitive lines, both impaired in ABA signaling without showing ABA-induced stress tolerance, were subjected to cold acclimation, and changes in freezing tolerance and accumulation of soluble sugars and proteins were compared to the wild type. The wild-type cells acquired freezing tolerance in response to cold acclimation treatment, but very little increase in freezing tolerance was observed in the ABA-insensitive lines. Analysis of low-molecular-weight soluble sugars indicated that the ABA-insensitive lines accumulated sucrose, a major compatible solute in bryophytes, to levels comparable with those of the wild type during cold acclimation. However, accumulation of the trisaccharide theanderose and of specific LEA-like boiling-soluble proteins was very limited in the ABA-insensitive lines. Furthermore, analysis of cold-induced expression of genes encoding LEA-like proteins revealed that the ABA-insensitive lines accumulate only small amounts of these transcripts during cold acclimation. Our results indicate that cold acclimation of bryophytes requires an ABA-dependent signaling process. The results also suggest that cold-induced sugar accumulation, depending on the sugar species, can either be dependent or independent of the ABA-signaling pathway.
越冬植物通过冷驯化过程发展对冷冻胁迫的耐受性，在此过程中细胞引发针对冷冻的内部保护机制。已知应激激素脱落酸（ABA）能提高植物细胞的抗冻性，但它在冷驯化中的作用尚未确定。在这项研究中，我们使用了藓类植物Physcomitrella patens 的 ABA 不敏感系，以确定苔藓植物的冷驯化是否涉及 ABA 依赖的过程。两种 ABA 不敏感系都在 ABA 信号中受损，而没有表现出 ABA 诱导的应激耐受性，它们被置于冷驯化条件下，然后比较其抗冻性变化以及可溶性糖和蛋白质的积累情况与野生型的差异。野生型细胞在冷驯化处理后获得了抗冻性，但 ABA 不敏感系的抗冻性几乎没有增加。对低分子量可溶性糖的分析表明，ABA 不敏感系积累了蔗糖，这是苔藓植物中的主要相容性溶质，在冷驯化期间其积累量可与野生型相当。然而，ABA 不敏感系中三糖棉子糖和特定 LEA 样沸腾可溶性蛋白的积累非常有限。此外，对编码 LEA 样蛋白的基因的冷诱导表达分析表明，ABA 不敏感系在冷驯化期间仅积累少量这些转录物。我们的结果表明，苔藓植物的冷驯化需要 ABA 依赖的信号过程。结果还表明，冷诱导的糖积累，取决于糖的种类，可以依赖于或独立于 ABA 信号通路。
