Tasmanian Institute of Agriculture, University of Tasmania, PO Box 3523, Burnie, TAS 7320, Australia.
AoB Plants. 2014 Apr 16;6(0). doi: 10.1093/aobpla/plu012. Print 2014.
The growth of fall dormant/freezing tolerant plants often surpasses the growth of non-fall dormant/non-freezing tolerant types of the same species under water-limited conditions, while under irrigated conditions non-fall dormant types exhibit superior yield performance. To investigate the mechanism behind this phenomenon, we exposed seven diverse alfalfa (Medicago sativa) cultivars to water-limited and fully watered conditions and measured their shoot growth, shoot water potential and gas exchange parameters and the relative abundance of taproot RNA transcripts associated with chilling stress/freezing tolerance. Fall dormant cultivars had greater shoot growth relative to the fully watered controls under a mild water deficit (a cumulative water deficit of 625 mL pot(-1)) and did not close their stomata until lower shoot water potentials compared with the more non-fall dormant cultivars. Several gene transcripts previously associated with freezing tolerance increased in abundance when plants were exposed to a mild water deficit. Two transcripts, corF (encodes galactinol synthase) and cas18 (encodes a dehydrin-like protein), increased in abundance in fall dormant cultivars only. Once water deficit stress became severe (a cumulative water deficit of 2530 mL pot(-1)), the difference between fall dormancy groups disappeared with the exception of the expression of a type 1 sucrose synthase gene, which decreased in fall dormant cultivars. The specific adaptation of fall dormant cultivars to mild water deficit conditions and the increase in abundance of specific genes typically associated with freezing tolerance in these cultivars is further evidence of a link between freezing tolerance/fall dormancy and adaption to drought conditions in this species.
休眠/抗冻植物在水分限制条件下的生长往往超过非休眠/非抗冻同种类型的生长，而在灌溉条件下，非休眠类型表现出更高的产量性能。为了研究这一现象的机制，我们将 7 种不同的紫花苜蓿（Medicago sativa）品种暴露在水分限制和充分浇水的条件下，测量了它们的枝条生长、枝条水势和气体交换参数以及与冷胁迫/抗冻性相关的主根 RNA 转录物的相对丰度。与充分浇水的对照相比，休眠品种在轻度水分亏缺（累计水分亏缺 625 毫升盆-1）下的枝条生长相对较高，并且与更非休眠品种相比，在较低的枝条水势下才关闭气孔。当植物暴露在轻度水分亏缺时，几种先前与抗冻性相关的基因转录物的丰度增加。两种转录物，corF（编码半乳糖醇合酶）和 cas18（编码脱水素样蛋白），仅在休眠品种中丰度增加。一旦水分亏缺胁迫变得严重（累计水分亏缺 2530 毫升盆-1），休眠组之间的差异除了 1 型蔗糖合酶基因的表达减少外，消失了，该基因在休眠品种中减少。休眠品种对轻度水分亏缺条件的特殊适应以及这些品种中与抗冻性相关的特定基因的丰度增加，进一步证明了抗冻性/休眠与该物种适应干旱条件之间存在联系。
