背景:在紫黄质(V)循环中,当强光或与其他应激源结合的光导致光系统的过度激发时,V被去环氧化为玉米黄质(Z)。然而,植物在黑暗中也会遭受压力,最近的报道表明,脱水会在没有光的情况下引发V-去环氧化。在这项研究中,我们使用高度耐受胁迫的褐藻Pelvetiacanaliculata作为模型生物,由于它缺乏叶黄素和它的非光化学猝灭独立于跨囊体-ΔpH,研究由非生物应激源诱导的黑暗中V循环的触发。
结果:我们已经表明,除了干燥,其他因素,如浸泡,缺氧和高温也会在黑暗中引起V-de环氧化。一旦治疗停止,这个过程是可逆的(除了加热,造成致命损害)。不考虑施加的压力,产生的去环氧化叶黄素与Fv/Fm的降低相关,表明在光合效率的下调中具有共同的功能。还研究了塑性醌池的氧化还原态和V循环酶对黑暗中V-去环氧化的差异活性的含义。目前的结果表明,即使在黑暗中,紫黄质去环氧酶(VDE)和玉米黄质-环氧酶(ZE)也具有基本的组成活性,在压力下被ZE抑制。这种抑制导致Z积累。
结论:这项研究表明,即使在绝对没有光的情况下,V周期活动也是由几种非生物应激源触发的。导致Fv/Fm降低。这一发现为了解V循环的调节机制及其生态生理作用提供了新的见解。
BACKGROUND: In the violaxanthin (V) cycle, V is de-epoxidized to zeaxanthin (Z) when strong light or light combined with other stressors lead to an overexcitation of photosystems. However, plants can also suffer stress in darkness and recent
reports have shown that dehydration triggers V-de-epoxidation in the absence of light. In this study, we used the highly stress-tolerant brown alga Pelvetia canaliculata as a model organism, due to its lack of lutein and its non-photochemical quenching independent of the transthylakoidal-ΔpH, to study the triggering of the V-cycle in darkness induced by abiotic stressors.
RESULTS: We have shown that besides desiccation, other factors such as immersion, anoxia and high temperature also induced V-de-epoxidation in darkness. This process was reversible once the treatments had ceased (with the exception of heat, which caused lethal damage). Irrespective of the stressor applied, the resulting de-epoxidised
xanthophylls correlated with a decrease in Fv/Fm, suggesting a common function in the down-regulation of photosynthetical efficiency. The implication of the redox-state of the plastoquinone-pool and of the differential activity of V-cycle enzymes on V-de-epoxidation in darkness was also examined. Current results suggest that both violaxanthin de-epoxidase (VDE) and zeaxanthin-epoxidase (ZE) have a basal constitutive activity even in darkness, being ZE inhibited under stress. This inhibition leads to Z accumulation.
CONCLUSIONS: This study demonstrates that V-cycle activity is triggered by several abiotic stressors even when they occur in an absolute absence of light, leading to a decrease in Fv/Fm. This finding provides new insights into an understanding of the regulation mechanism of the V-cycle and of its ecophysiological roles.