外源γ-氨基丁酸缓解番茄幼苗热胁迫的生理生化机制

Physiological and biochemical mechanism of exogenousγ-aminobutyric acid alleviating heat stress in tomato seedlings

高温是番茄(Solanum lycopersicum)面临的主要非生物胁迫之一,严重影响番茄的生长发育、产量和品质。γ-氨基丁酸(GABA)能够有效调节植物对非生物胁迫的耐受性。以热敏感型番茄作为试验材料进行高温处理,结果显示外施GABA能够显著提高番茄幼苗的耐热性。与对照组叶片严重萎蔫的状态相比,GABA处理组的番茄植株呈现正常的生长状态。GABA处理有效缓解高温对番茄叶片光合系统造成的损伤,最大光化学效率(Fv/Fm)是对照组的2.27倍,叶绿素a、b及总叶绿素含量均显著高于对照组。外源GABA提高了番茄幼苗的过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性,显著降低了丙二醛(MDA)、过氧化氢(H_(2)O_(2))和超氧阴离子(O^(-)·_(2))含量,增加了游离脯氨酸(Pro)、可溶性糖(SS)和多胺(PA)类物质的积累量。分子水平检测结果表明,外源GABA能够显著上调热胁迫响应基因、抗氧化相关基因、多胺合成基因的表达量,降低热休克蛋白基因、多胺降解基因的表达量。基因表达水平与GABA提高番茄幼苗耐热性的表型特征一致。综上结果表明,外源GABA可以调控植物体内复杂的生物学过程进而缓解热胁迫对番茄幼苗造成的损伤。

High temperature is one of the main abiotic stresses faced by tomato(Solanum lycopersicum).Heat stress severely affects tomato growth and development,as well as crop yield and quality.Γ-aminobutyric acid(GABA)was reported to play a pivotal role in regulating plant tolerance to abiotic stresses.The tomato seedlings were treated with exogenous GABA,and then were treated under heat stress.The results show that exogenous GABA can alleviate the damage induced by heat stress and keep the tomato plants growing normally under high temperature conditions.Under high temperature stress,the maximum photochemical efficiency(F_v/F_m)was 2.27 times than that of the control group,and the contents of chlorophyll a,chlorophyll b and total chlorophyll were significantly higher than those of the control group.Tomato seedlings treated with GABA had higher activities of peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT).The contents of malondialdehyde(MDA),hydrogen peroxide(H_(2)O_(2))and superoxide anion (O^(-)·_(2)) treated with GABA were significantly reduced,while higher free proline(Pro),soluble sucrose(SS)and polyamine(PA)were accumulated under heat stress.Additionally,the results of gene expression level show that exogenous GABA positively regulated the heat stress–response,antioxidation-related,and polyamine synthesis genes in the tomato seedlings.Meanwhile,exogenous GABA negatively regulated the heat shock protein genes,and polyamine-degrading genes in the tomato seedlings.In conclusion,exogenous GABA significantly alleviated the damage of tomato seedlings at high temperature by regulating complex biological processes.