title: Drought-inhibited ribulose-1,5-bisphosphate carboxylase activity is mediated through increased release of ethylene and changes in the ratio of polyamines in pakchoi.
abstract: To study the mechanisms of drought inhibiting photosynthesis and the role of PAs and ethylene, the photosynthetic rate (Pn), the maximal photochemical efficiency of PSII (Fv/Fm), the intercellular CO2 concentration (Ci), photorespiratory rate (Pr), the amount of chlorophyll (chl), antioxidant enzyme activity, ethylene levels, RuBPC (ribulose-1,5-bisphosphate carboxylase) activity and endogenous polyamine levels of pakchoi were examined, and an inhibitor of S-adenosylmethionine decarboxylase (SAMDC) and an inhibitor of ethylene synthesis and spermidine (Spd) were used to induce the change of endogenous polyamine levels. The results show that drought induced a decrease in Pn and RuBPC activity, an increase in the intercellular CO2 concentration (Ci), but no change in the actual photochemical efficiency of PSII (ΦPSII), and chlorophyll content. In addition, drought caused an increase in the free putrescine (fPut), the ethylene levels, a decrease in the Spd and spermine (Spm) levels, and the PAs/fPut ratio in the leaves. The exogenous application of Spd and amino oxiacetic acid (AOAA, an inhibitor of ethylene synthesis) markedly reversed these drought-induced effects on polyamine, ethylene, Pn, the PAs/fPut ratio and RuBPCase activity in leaves. Methylglyoxal-bis(guanylhydrazone) (MGBG), an inhibitor of SAMDC resulting in the inability of activated cells to synthesize Spd and Spm, exacerbates the negative effects induced by drought. These results suggest that the decrease in Pn is at least partially attributed to the decrease of RuBPC activity under drought stress and that drought inhibits RuBPC activity by decreasing the ratio of PAs/fPut and increasing the release of ethylene.
authors.affiliation: Wuhan Institute of Vegetable Science, Wuhan 430345, China.
authors.forename: Xingxue
authors.initials: X
authors.lastname: Huang
authors.affiliation: Wuhan Institute of Vegetable Science, Wuhan 430345, China. Electronic address: hxx329517@126.com.
authors.forename: Guolin
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Wuhan Meteorologic Bureau, Wuhan 430040, China.
authors.forename: Wengang
authors.initials: W
authors.lastname: Yang
authors.affiliation: Wuhan Institute of Vegetable Science, Wuhan 430345, China.
authors.forename: Aihua
authors.initials: A
authors.lastname: Wang
authors.affiliation: Wuhan Institute of Vegetable Science, Wuhan 430345, China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Wuhan Institute of Vegetable Science, Wuhan 430345, China.
authors.forename: Chufa
authors.initials: C
authors.lastname: Lin
authors.affiliation: Wuhan Meteorologic Bureau, Wuhan 430040, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D029741:Brassica rapa / Q000201:enzymology / Q000502:physiology*; D055864:Droughts; D005030:Ethylenes / Q000378:metabolism*; D010788:Photosynthesis; D010937:Plant Growth Regulators / Q000378:metabolism*; D011073:Polyamines / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D012274:Ribulosephosphates / Q000378:metabolism
chemical_list: D000975:Antioxidants; D005030:Ethylenes; D010937:Plant Growth Regulators; D011073:Polyamines; D012274:Ribulosephosphates; C001933:ribulose-1,5 diphosphate; C036216:ethylene; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Antioxidant enzyme; Drought; Ethylene; Photosynthesis; Polyamine