Abstract：
Isoprenoid metabolism and its derivatives took part in photosynthesis, growth regulation, signal transduction, and plant defense to biotic and abiotic stresses. However, how aluminum (Al) stress affects the isoprenoid metabolism and whether isoprenoid metabolism plays a vital role in the Citrus plants in coping with Al stress remain unclear. In this study, we reported that Al-treatment-induced alternation in the volatilization rate of monoterpenes (α-pinene, β-pinene, limonene, α-terpinene, γ-terpinene and 3-carene) and isoprene were different between Citrus sinensis (Al-tolerant) and C. grandis (Al-sensitive) leaves. The Al-induced decrease of CO2 assimilation, maximum quantum yield of primary PSII photochemistry (Fv/Fm), the lower contents of glucose and starch, and the lowered activities of enzymes involved in the mevalonic acid (MVA) pathway and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway might account for the different volatilization rate of isoprenoids. Furthermore, the altered transcript levels of genes related to isoprenoid precursors and/or derivatives metabolism, such as geranyl diphosphate (GPP) synthase (GPPS) in GPP biosynthesis, geranylgeranyl diphosphate synthase (GGPPS), chlorophyll synthase (CHS) and GGPP reductase (GGPPR) in chlorophyll biosynthesis, limonene synthase (LS) and α-pinene synthase (APS) in limonene and α-pinene synthesis, respectively, might be responsible for the different contents of corresponding products in C. grandis and C. sinensis. Our data suggested that isoprenoid metabolism was involved in Al tolerance response in Citrus, and the alternation of some branches of isoprenoid metabolism could confer different Al-tolerance to Citrus species.
摘要：
类异戊二烯代谢及其衍生物参与光合作用，生长调节，信号转导，和植物防御生物和非生物胁迫。然而,铝（Al）胁迫如何影响类异戊二烯代谢以及类异戊二烯代谢在柑橘植物应对Al胁迫中起着至关重要的作用尚不清楚。在这项研究中,我们报道了铝处理引起的单萜（α-pine烯，β-pine烯,柠檬烯,α-萜品烯,柑橘（耐铝）和C.grandis（铝敏感）叶片之间的γ-松油烯和3-carene）和异戊二烯不同。Al诱导的CO2同化减少，初级PSII光化学的最大量子产率（Fv/Fm），葡萄糖和淀粉含量较低，与甲羟戊酸（MVA）途径和2-C-甲基-D-赤藓糖醇4-磷酸（MEP）途径有关的酶活性降低可能是类异戊二烯挥发速率不同的原因。此外，与类异戊二烯前体和/或衍生物代谢相关的基因的转录水平改变，如叶酰二磷酸（3GPP）合成酶（GPPS）在GMP生物合成，香叶基香叶基二磷酸合成酶（GGPPS），叶绿素合成酶（CHS）和GPB还原酶（GGPPR）在叶绿素生物合成中，柠檬烯合酶（LS）和α-pine烯合酶（APS）在柠檬烯和α-pine烯合成中，分别,可能是C.grandis和C.sinensis中相应产品含量不同的原因。我们的数据表明类异戊二烯代谢参与柑橘的铝耐受反应，类异戊二烯代谢的某些分支的交替可以赋予柑橘不同的耐铝能力。
