Key Laboratory of Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610064, China.
Plant Cell Physiol. 2017 Nov 1;58(11):1976-1990. doi: 10.1093/pcp/pcx140.
Boea hygrometrica (B. hygrometrica) can tolerate severe desiccation and resume photosynthetic activity rapidly upon water availability. However, little is known about the mechanisms by which B. hygrometrica adapts to dehydration and resumes competence upon rehydration. Here we determine how B. hygrometrica deals with oxidative stress, excessive excitation/electron pressures as well as photosynthetic apparatus modulation during dehydration/rehydration. By measuring ROS generation and scavenging efficiency, we found that B. hygrometrica possesses efficient strategies to maintain cellular redox homeostasis. Transmission electron microscopy (TEM) analysis revealed a remarkable alteration of chloroplast architecture and plastoglobules (PGs) accumulation during dehydration/rehydration. Pulse-amplitude modulated (PAM) chlorophyll fluorescence measurements, P700 redox assay as well as chlorophyll fluorescence emission spectra analysis on leaves of B. hygrometrica during dehydration/rehydration were also performed. Results showed that the photochemical activity of PSII as well as photoprotective energy dissipation in PSII undergo gradual inactivation/activation during dehydration/rehydration in B. hygrometrica; PSI activity is relatively induced upon water deficit, and dehydration leads to physical interaction between PSI and LHCII. Furthermore, blue-native polyacrylamide gel electrophoresis (BN-PAGE) and immunoblot analysis revealed that the protein abundance of light harvesting complexes decrease markedly along with internal water deficit to restrict light absorption and attenuate electron transfer, resulting in limited light excitation and repressed photosynthesis. In contrast, many thylakoid proteins remain at a basal level even after full dehydration. Taken together, our study demonstrated that efficient modulation of cellular redox homeostasis and photosynthetic activity confers desiccation tolerance in B. hygrometrica.
波叶海桑（Boea hygrometrica）能够耐受严重的干旱，并在水分供应时迅速恢复光合作用。然而，人们对波叶海桑适应干旱和再水合时恢复活力的机制知之甚少。在这里，我们确定了波叶海桑在脱水和再水合过程中如何应对氧化应激、过度激发/电子压力以及光合作用装置的调节。通过测量 ROS 的产生和清除效率，我们发现波叶海桑具有维持细胞氧化还原平衡的有效策略。透射电子显微镜（TEM）分析显示，在脱水/再水合过程中，叶绿体结构和质体小球（PGs）积累发生显著改变。还对波叶海桑叶片在脱水/再水合过程中的脉冲幅度调制（PAM）叶绿素荧光测量、P700 氧化还原测定以及叶绿素荧光发射光谱分析进行了研究。结果表明，在波叶海桑的脱水/再水合过程中，PSII 的光化学活性以及 PSII 中的光保护能量耗散逐渐失活/激活；PSI 活性在水分亏缺时相对诱导，而脱水导致 PSI 和 LHCII 之间发生物理相互作用。此外，蓝-Native 聚丙烯酰胺凝胶电泳（BN-PAGE）和免疫印迹分析表明，随着内部水分亏缺，光捕获复合物的蛋白丰度显著降低，从而限制光吸收并减弱电子传递，导致有限的光激发和受抑的光合作用。相比之下，许多类囊体蛋白即使在完全脱水后仍保持在基础水平。综上所述，我们的研究表明，有效的细胞氧化还原平衡和光合作用调节赋予了波叶海桑耐旱性。
