Department of Botany, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization-Dimitra, GR-57001 Thessaloniki, Greece.
Int J Mol Sci. 2023 May 31;24(11):9573. doi: 10.3390/ijms24119573.
Since drought stress is one of the key risks for the future of agriculture, exploring the molecular mechanisms of photosynthetic responses to water deficit stress is, therefore, fundamental. By using chlorophyll fluorescence imaging analysis, we evaluated the responses of photosystem II (PSII) photochemistry in young and mature leaves of Col-0 (cv Columbia-0) at the onset of water deficit stress (OnWDS) and under mild water deficit stress (MiWDS) and moderate water deficit stress (MoWDS). Moreover, we tried to illuminate the underlying mechanisms in the differential response of PSII in young and mature leaves to water deficit stress in the model plant . Water deficit stress induced a hormetic dose response of PSII function in both leaf types. A U-shaped biphasic response curve of the effective quantum yield of PSII photochemistry (Φ) in young and mature leaves was observed, with an inhibition at MiWDS that was followed by an increase in Φ at MoWDS. Young leaves exhibited lower oxidative stress, evaluated by malondialdehyde (MDA), and higher levels of anthocyanin content compared to mature leaves under both MiWDS (+16%) and MoWDS (+20%). The higher Φ of young leaves resulted in a decreased quantum yield of non-regulated energy loss in PSII (Φ), under both MiWDS (-13%) and MoWDS (-19%), compared to mature leaves. Since Φ represents singlet-excited oxygen (O) generation, this decrease resulted in lower excess excitation energy at PSII, in young leaves under both MiWDS (-10%) and MoWDS (-23%), compared to mature leaves. The hormetic response of PSII function in both young and mature leaves is suggested to be triggered, under MiWDS, by the intensified reactive oxygen species (ROS) generation, which is considered to be beneficial for activating stress defense responses. This stress defense response that was induced at MiWDS triggered an acclimation response in young leaves and provided tolerance to PSII when water deficit stress became more severe (MoWDS). We concluded that the hormesis responses of PSII in under water deficit stress are regulated by the leaf developmental stage that modulates anthocyanin accumulation in a stress-dependent dose.
由于干旱胁迫是未来农业的关键风险之一，因此探索光合作用对水分亏缺胁迫的分子机制至关重要。通过使用叶绿素荧光成像分析，我们评估了 Col-0（cv Columbia-0）幼叶和成熟叶在水分亏缺胁迫开始时（OnWDS）和轻度水分亏缺胁迫（MiWDS）和中度水分亏缺胁迫（MoWDS）下 PSII 光化学的响应。此外，我们试图在模式植物中阐明 PSII 在幼叶和成熟叶对水分亏缺胁迫的差异响应中的潜在机制。水分亏缺胁迫诱导了两种叶片类型 PSII 功能的兴奋剂量反应。在幼叶和成熟叶中，PSII 光化学有效量子产率（Φ）的 U 型双相响应曲线观察到，在 MiWDS 下抑制，随后在 MoWDS 下增加。与成熟叶相比，在 MiWDS（+16%）和 MoWDS（+20%）下，幼叶表现出较低的氧化应激，用丙二醛（MDA）评估，以及较高的花色素苷含量。与成熟叶相比，在 MiWDS（-13%）和 MoWDS（-19%）下，幼叶的较高Φ导致 PSII 中非调节能量损失的量子产率（Φ）降低。由于 Φ 代表单重激发氧（O）的产生，因此这种减少导致 PSII 中过量激发能降低，在 MiWDS（-10%）和 MoWDS（-23%）下的幼叶与成熟叶相比。在 MiWDS 下，PSII 功能的兴奋反应被认为是由活性氧（ROS）生成的加剧引发的，这被认为有利于激活应激防御反应。这种在 MiWDS 下诱导的应激防御反应在幼叶中引发了适应反应，并在水分亏缺胁迫变得更加严重（MoWDS）时为 PSII 提供了耐受性。我们得出结论，PSII 在水分亏缺胁迫下的兴奋反应受叶片发育阶段调节，该阶段以应激依赖剂量调节花色素苷积累。
