从光合作用和有机酸积累角度探索转GsPPCK1和GsPPCK3基因苜蓿耐碱性增强的生理机制

doi:10.11686/cyxb2017391

摘要/Abstract

摘要： 光合作用影响着植物的生长发育及产量,并在盐碱胁迫响应中起到积极作用。前期研究将光合途径中野生大豆来源的GsPPCK1和GsPPCK3基因转入苜蓿,所获得转基因苜蓿耐碱性提高。从光合作用和有机酸积累角度探索转GsPPCK1和GsPPCK3基因苜蓿耐碱性增强的生理机制。结果表明,碱胁迫9 d后,叶绿素的相对含量下降,转基因株系P1-5、P3-8与未处理相比变化并不显著,分别下降了11.27%、13.30%,而非转基因株系的叶绿素含量下降了39.11%。转基因株系P1-5、P3-8光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)及胞间CO₂浓度(C_i)在胁迫处理后也有下降趋势,但下降的幅度仅为非转基因植株下降幅度的1/2。光合途径中NADP-苹果酸脱氢酶、NADP-苹果酸酶、磷酸烯醇式丙酮酸羧化酶、丙酮酸正磷酸二激酶、核酮糖-1,5-二磷酸羧化酶等关键酶的酶活及有机酸(苹果酸、柠檬酸、草酰乙酸、磷酸烯醇式丙酮酸)含量在碱胁迫处理后均呈上升趋势,而转基因株系P1-5、P3-8 的光合酶活和4种有机酸含量与非转基因对照相比上升极显著(P<0.01)。PEPC(Medtr4g079860.1)、NADP-ME(Medtr8g014390.1)、NADP-MDH(Medtr1g043040.1)、PPDK(Medtr4g118350.1)及Rubisco(Medtr4g 021210.1)基因的表达呈先上升后下降趋势,转基因株系中基因的表达变化较非转基因对照更为显著(P<0.01)。由此表明,在正常情况下,GsPPCK1和GsPPCK3基因的超量表达并未影响植物的光合作用,但是在碱胁迫下,转基因苜蓿的光合作用受碱胁迫的抑制较小,这一过程可能与PEPC酶的激活有关。另外,光合中间产物有机酸含量的显著上升对维持细胞内pH值的稳定也起到重要作用。

关键词: GsPPCKs, 耐碱性, 转基因苜蓿, 光合效率, 有机酸

Abstract: Photosynthesis affects the growth and development of plants including their response to salt and alkali stress. Previous studies have shown that over-expression of GsPPCK1 or GsPPCK3 from Glycine soja in alfalfa resulted in enhanced plant tolerance to alkali stress. Here, physiological and biochemical indexes and gene expression related traits were investigated to explore the physiological mechanism of alkali-resistant transgenic alfalfa from the perspective of photosynthesis and organic acid accumulation. The chlorophyll content of transgenic lines P1-5 and P3-8 were not different from untreated plants after 9 days of alkali exposure, decreasing by 11.27% and 13.30% respectively, while that of non-transgenic lines decreased by 39.11%. The photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) of transgenic lines P1-5 and P3-8 all decreased after alkali exposure, but the decreased was half that of non-transgenic plants. NADP-malate dehydrogenase, NADP-malic enzyme, phosphoenolpyruvate carboxylase, pyruvate orthophosphate dikinase, ribulose-1,5-bisphosphate carboxylase enzyme activity and organic acid content (malic acid, citric acid, oxaloacetic acid and phosphoenolpyruvate) trended upward after alkali treatment. The photosynthetic enzyme activity and organic acid content of transgenic lines P1-5 and P3-8 were significantly different (P<0.01) from non-transgenic plants. The expression of PEPC (Medtr4g079860.1), NADP-ME (Medtr8g014390.1), NADP-MDH (Medtr1g043040.1), PPDK (Medtr4g118350.1) and Rubisco (Medtr4g021210.1) were induced under alkali stress and subsequently declined, the expression level in transgenic lines was greater than non-transgenic lines. The results indicated that under normal conditions, the overexpression of GsPPCK1 or GsPPCK3 did not improve photosynthesis of transgenic lines, but photosynthesis in transgenic alfalfa was less affected by alkali stress. This process may be related to the activity of PEPC. In addition, a significant increase in organic acid content played an important role in stabilizing intracellular pH.

Key words: GsPPCKs, alkali stress, transgenic alfalfa, photosynthetic efficiency, organic acid

才华, 许慧慧, 孙娜, 宋婷婷, 任永晶, 杨圣秋. 从光合作用和有机酸积累角度探索转GsPPCK1和GsPPCK3基因苜蓿耐碱性增强的生理机制[J]. 草业学报, 2018, 27(8): 107-117.

CAI Hua, XU Hui-hui, SUN Na, SONG Ting-ting, REN Yong-jing, YANG Sheng-qiu. Physiological aspects of photosynthesis and organic acid accumulation in alkali-resistant transgenic alfalfa containing the GsPPCK1 and GsPPCK3 genes[J]. Acta Prataculturae Sinica, 2018, 27(8): 107-117.

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