Yang Si-Yu, Wu Yu-Sian, Chen Chung-Tse, Lai Ming-Hsin, Yen Hsing-Mu, Yang Chin-Ying
Department of Agronomy, National Chung Hsing University, Taichung, 40227, Taiwan.
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan.
Rice (N Y). 2017 Aug 31;10(1):42. doi: 10.1186/s12284-017-0180-3.
Understanding the responses of rice to environmental stresses such as unscheduled submergence is of pressing important owing to increasing severity of weather thought to arise from global climate change. When rice is completely submerged, different types adopt either a quiescence survival strategy (i.e., minimal shoot elongation) or an escape strategy (i.e., enhanced shoot elongation). Each strategy can prolong survival depending on the circumstances. While submergence responses have been studied in rice typical of lowland and flood-prone areas, few studies have explored the physiological and molecular properties of upland rice under submergence. Here, we use seedlings of the upland rice 'Tung Lu 3' ('TL3') to analyze physiological and molecular responses to submergence. We compare them with those of 'FR13A', a lowland rice that tolerates submergence by adopting the quiescence strategy.
Plant height and distance between leaf sheaths, increased rapidly in 'TL3' under submergence. Although this indicated a strong escape strategy the seedlings remained totally underwater for the duration of the experiments. In contrast, 'FR13A' elongated much less. Consequently, after 4 days complete submergence followed by drainage, 'TL3' lodged much more severely than 'FR13A'. After 10 d complete submergence, 55% of 'TL3' seedlings survived compared to 100% in 'FR13A'. Chlorophyll a, b and total chlorophyll concentrations of the 2 oldest leaves of 'TL3' were also significantly above those of 'FR13A' (but were lower than 'FR13A' in the 3 oldest leaves) and less hydrogen peroxide accumulated in 'TL3'. Peroxidase activity in submerged 'TL3' was also greater than in 'FR13A' 1 day after submergence. Quantitative RT-PCR showed increased expression of sucrose synthase 1 and alcohol dehydrogenases 1 after 2 days complete submergence with significantly higher levels in 'TL3' compared to 'FR13A'. Expression was also higher in 'TL3' under non-submerged conditions.
The upland rice line 'TL3' gave a stronger elongation response than 'FR13A' to complete submergence. This escape strategy is widely considered to prejudice survival when the plant remains totally submerged. However, contrary to expectations, 'TL3' survival rates were substantial although below those for 'FR13A' while physiological, biochemical and molecular parameters linked to adaptation differed in detail but appeared to be broadly comparable. These findings highlight that submergence tolerance is determine not only by the adoption of quiescence or escape strategies but maybe by metabolic and physiological properties unrelated to the underwater elongation rate.
鉴于全球气候变化导致天气状况愈发恶劣，了解水稻对诸如意外淹水等环境胁迫的响应至关重要。当水稻完全被淹没时，不同类型的水稻会采取静止存活策略（即最小化地上部分伸长）或逃避策略（即增强地上部分伸长）。每种策略都可根据具体情况延长存活时间。虽然已经对典型的低地和易涝地区水稻的淹水响应进行了研究，但很少有研究探讨淹水条件下旱稻的生理和分子特性。在此，我们使用旱稻品种‘通陆3号’（‘TL3’）的幼苗来分析其对淹水的生理和分子响应。我们将其与‘FR13A’进行比较，‘FR13A’是一种通过采取静止策略来耐受淹水的低地水稻。
淹水条件下，‘TL3’的株高和叶鞘间距迅速增加。尽管这表明其具有强烈的逃避策略，但在整个实验期间幼苗仍完全处于水下。相比之下，‘FR13A’的伸长幅度要小得多。因此，在完全淹水4天后排水，‘TL3’的倒伏情况比‘FR13A’严重得多。完全淹水10天后，‘TL3’幼苗的存活率为55%，而‘FR13A’为100%。‘TL3’最老的两片叶子的叶绿素a、b和总叶绿素浓度也显著高于‘FR13A’（但最老的三片叶子中的浓度低于‘FR13A’），且‘TL3’中积累的过氧化氢较少。淹水1天后，淹水的‘TL3’中的过氧化物酶活性也高于‘FR13A’。定量逆转录聚合酶链反应显示，完全淹水2天后，蔗糖合酶1和乙醇脱氢酶1的表达增加，‘TL3’中的水平显著高于‘FR13A’。在非淹水条件下，‘TL3’中的表达也较高。
旱稻品系‘TL3’对完全淹水的伸长响应比‘FR13A’更强。当植株完全被淹没时，这种逃避策略通常被认为不利于存活。然而，与预期相反，‘TL3’虽然存活率低于‘FR13A’，但仍相当可观，而与适应相关的生理、生化和分子参数虽细节不同，但总体上似乎具有可比性。这些发现表明，耐淹性不仅取决于采取静止或逃避策略，还可能取决于与水下伸长率无关的代谢和生理特性。
