低温胁迫对狗牙根生理及基因表达的影响

以耐寒性差异较大的杂交狗牙根品种运动百慕大、天堂419和普通狗牙根品种保定狗牙根为试验材料,分析了昼夜温度为适温(30 ℃/25 ℃)、亚适温(18 ℃/12 ℃)、冷害(8 ℃/4 ℃)和冻害(4 ℃/-4 ℃)4种温度处理下,低温对狗牙根生长速率和草坪质量、MDA含量、叶绿素荧光(F_v/F_m)、光合作用(P_n、G_s、C_i、T_r)、H₂O₂和O2·-含量、抗氧化酶活性(SOD、POD、CAT、APX)、抗氧化酶及耐寒相关基因(CBF1、COR、LEA)表达的影响。结果表明,随着温度的降低,狗牙根草坪质量、生长速率、F_v/F_m和光合作用显著下降,但在耐寒性强的运动百慕大中下降幅度较小;低温下叶片MDA和H₂O₂含量及O2·-产生速率显著升高,其中在耐寒性弱的保定狗牙根中升高程度更大;狗牙根叶片抗氧化酶活性及抗氧化酶基因的表达水平随着处理温度的下降而显著升高,其中在运动百慕大中更为明显;狗牙根CBF1、COR和LEA基因表达量随着温度的下降而显著升高,尤其是在耐寒狗牙根运动百慕大中更为显著。低温诱导的抗氧化酶和耐寒相关基因上调表达,增强了细胞内的抗氧化防御,有助于狗牙根植株维持较高的光合作用和细胞膜稳定性,延缓叶片的衰老,从而提高了狗牙根的抗寒能力。

Effect of low temperature stress on physiology and gene expression in Bermuda grass

In order to investigate the effects of low temperature stress on the plant growth rate, turf quality, MDA content, F_v/F_m, photosynthesis [P_n (net photosynthetic rate); G_s (stomatal conductance); C_i (intercellular CO₂ concentration); T_r (transpiration rate)], H₂O₂ and O2·- content, antioxidant enzyme activities (SOD, POD, CAT, APX), gene expression levels of antioxidant enzymes and cold-tolerance related genes (CBF1, COR, LEA), three Bermudagrass cultivars with differential cold tolerance, Tifsport, Tifway and Baoding Bermuda grass were selected and treated under a range of temperatures: optimum (30 ℃/25 ℃, day/night), suboptimum (18 ℃/12 ℃), chilling (8 ℃/4 ℃) and freezing (4 ℃/-4 ℃) in growth chambers. It was found that plant growth rate, turf quality, F_v/F_m and photosynthesis decreased while H₂O₂, MDA content and O2·- production rate increased with reduction in temperature, but the three cultivars varied in their response, with more rapid changes in the less cold-tolerant Baoding Bermuda grass. Leaf antioxidant enzyme activities were significantly increased with reduction in temperature, especially in the more cold-tolerant Tifsport. Similarly, the expression levels of CBF1, COR and LEA cold-tolerance genes were also significantly enhanced with decline in temperature, with Tifsport again exhibiting the greatest response. In summary, low temperature stress induced up-regulation of antioxidant enzyme genes and cold tolerance-related genes resulting in more active antioxidant defense systems, which in turn contributed to improved cell membrane stability, maintenance of higher photosynthesis levels and delay of chlorosis in Bermuda grass. These changes collectively were the basis for the higher cold tolerance.