水稻叶绿体抗坏血酸过氧化物酶在干旱和高盐胁迫中的作用

Function of Rice Chloroplastic Ascorbate Peroxidases in Drought and Salt Stress Conditions

逆境条件下植物积累大量包括过氧化氢(H_2O_2)在内的活性氧。抗坏血酸过氧化物酶(APX)能分解H_2O_2,被认为在植物逆境胁迫中发挥着重要作用。水稻APX家族有8个成员,有关叶绿体APX7(基质型)、APX8(类囊体型)在逆境中的功能鲜见报道。本研究以从水稻T-DNA插入突变库中筛选出的Osapx7和Osapx8突变体为材料,在停止浇水和150 mmol·L-1NaCl处理14 d后,与野生型相比,Osapx7和Osapx8的生长均受到抑制,叶片萎蔫严重,但难以从直观上辨别出两者之间的区别。干旱条件下,与野生型相比,突变体植株叶片内H_2O_2含量升高,叶片DAB染色加深,叶绿素含量和相对水含量下降;而在150 mmol·L^(-1) NaCl条件下,突变体与野生型之间这些指标区别不大。除干旱条件下Osapx8的相对含水量低于Osapx7外,两者的形态与其他生理指标的变化基本相当。这些结果表明,水稻叶绿体APXs,特别是APX8在水稻对抗干旱逆境中发挥着重要的作用。

Plants accumulate a substantial amount of reactive oxide species（ROS） including hydrogen peroxide（H2O2） under stress conditions. Ascorbate peroxidases（APX）, which catalyze the decomposation of H2O2, is thought to play important roles in plant stress response. Rice APX family has eight members, there is little information about the function of chloroplast APX7（stroma APX） and APX8（thylakoid-bound APX） in stress response. On the basis of rice Osapx7 and Osapx8 mutants screened from a T-DNA insertion mutagenesis library, we treated the genotypes without watering or watering with 150 mmol·L^（-1） NaCl for 14 days. Osapx7 and Osapx8 were significantly inhibited their growth and showed a more severe wilting phenotype compared with wild type. However, it is hard to tell the differences between the mutants from the morphological observation.Under drought stress, the leaves of mutant plants accumulated more H2O2 with a darker color in DAB staining,decreased the chlorophyll contents and relative water contents; while under 150 mmol·L^（-1） NaCl, no significant differences were shown in these indexes between wild type and these mutants. Except that Osapx8 had a lower relative water content than Osapx7 under drought stress, their morphological and physiological index were roughly similar. These data suggested that chloroplast APXs, particularly APX8, play an important role in drought stress in rice.