Department of Molecular Biology, Sejong University, Seoul 05006, South Korea.
Department of Agricultural Biotechnology, National Institute of Agricultural Science, Rural Development Administration, Jeonju 54874, South Korea.
Plant Physiol. 2022 Jun 27;189(3):1363-1379. doi: 10.1093/plphys/kiac166.
Fibrillins (FBNs) are the major structural proteins of plastoglobules (PGs) in chloroplasts. PGs are associated with defense against abiotic and biotic stresses, as well as lipid storage. Although FBN2 is abundant in PGs, its independent function under abiotic stress has not yet been identified. In this study, the targeting of FBN2 to PGs was clearly demonstrated using an FBN2-YFP fusion protein. FBN2 showed higher expression in green photosynthetic tissues and was upregulated at the transcriptional level under high-light stress. The photosynthetic capacity of fbn2 knockout mutants generated using CRISPR/Cas9 technology decreased rapidly compared with that of wild-type (WT) plants under high-light stress. In addition to the photoprotective function of FBN2, fbn2 mutants had lower levels of plastoquinone-9 and plastochromanol-8. The fbn2 mutants were highly sensitive to methyl jasmonate (MeJA) and exhibited root growth inhibition and a pale-green phenotype due to reduced chlorophyll content. Consistently, upon MeJA treatment, the fbn2 mutants showed faster leaf senescence and more rapid chlorophyll degradation with decreased photosynthetic ability compared with the WT plants. The results of this study suggest that FBN2 is involved in protection against high-light stress and acts as an inhibitor of jasmonate-induced senescence in Arabidopsis (Arabidopsis thaliana).
纤维连接蛋白（FBNs）是质体小球（PGs）中的主要结构蛋白。PGs 与抗非生物和生物胁迫以及脂质储存有关。虽然 FBN2 在 PGs 中含量丰富，但它在非生物胁迫下的独立功能尚未确定。在这项研究中，使用 FBN2-YFP 融合蛋白清楚地证明了 FBN2 靶向 PGs。FBN2 在绿色光合组织中表达较高，在高光胁迫下转录水平上调。使用 CRISPR/Cas9 技术生成的 fbn2 敲除突变体的光合能力在高光胁迫下比野生型（WT）植物迅速下降。除了 FBN2 的光保护功能外，fbn2 突变体的质体醌-9 和质体色醇-8 水平较低。fbn2 突变体对茉莉酸甲酯（MeJA）高度敏感，由于叶绿素含量降低，表现出根生长抑制和浅绿色表型。一致地，在 MeJA 处理下，与 WT 植物相比，fbn2 突变体表现出更快的叶片衰老和更快的叶绿素降解，光合能力下降。这项研究的结果表明，FBN2 参与了对高光胁迫的保护，并作为拟南芥（Arabidopsis thaliana）中茉莉酸诱导衰老的抑制剂。
