Centro de Biotecnologia e Genética, Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Ilhéus, Bahia, Brazil.
Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
PLoS One. 2022 Sep 16;17(9):e0274791. doi: 10.1371/journal.pone.0274791. eCollection 2022.
Galactinol synthase (GolS) catalyzes the first and rate-limiting step in the synthesis of raffinose family of oligosaccharides (RFOs), which serve as storage and transport sugars, signal transducers, compatible solutes and antioxidants in higher plants. The present work aimed to assess the potential functions of citrus GolS in mechanisms of stress response and tolerance. By homology searches, eight GolS genes were found in the genomes of Citrus sinensis and C. clementina. Phylogenetic analysis showed that there is a GolS ortholog in C. clementina for each C. sinensis GolS, which have evolved differently from those of Arabidopsis thaliana. Transcriptional analysis indicated that most C. sinensis GolS (CsGolS) genes show a low-level tissue-specific and stress-inducible expression in response to drought and salt stress treatments, as well as to 'Candidatus Liberibacter asiaticus' infection. CsGolS6 overexpression resulted in improved tobacco tolerance to drought and salt stresses, contributing to an increased mesophyll cell expansion, photosynthesis and plant growth. Primary metabolite profiling revealed no significant changes in endogenous galactinol, but different extents of reduction of raffinose in the transgenic plants. On the other hand, a significant increase in the levels of metabolites with antioxidant properties, such as ascorbate, dehydroascorbate, alfa-tocopherol and spermidine, was observed in the transgenic plants. These results bring evidence that CsGolS6 is a potential candidate for improving stress tolerance in citrus and other plants.
半乳糖苷蔗糖合酶（GolS）催化棉子糖家族低聚糖（RFOs）合成的第一步和限速步骤，RFOs 作为高等植物的储存和运输糖、信号转导物、相容性溶质和抗氧化剂。本研究旨在评估柑橘 GolS 在应激响应和耐受机制中的潜在功能。通过同源性搜索，在甜橙（Citrus sinensis）和克莱门氏小柑橘（C. clementina）的基因组中发现了 8 个 GolS 基因。系统发育分析表明，克莱门氏小柑橘中有一个 GolS 直系同源物对应于甜橙的每个 GolS，这些基因从进化上与拟南芥的 GolS 不同。转录分析表明，大多数甜橙 GolS（CsGolS）基因在受到干旱和盐胁迫处理以及“亚洲韧皮杆菌”感染时，表现出低水平的组织特异性和诱导表达。CsGolS6 的过表达导致烟草对干旱和盐胁迫的耐受性提高，有助于增加叶肉细胞的扩张、光合作用和植物生长。初级代谢物分析显示内源半乳糖醇没有显著变化，但转基因植物中棉子糖的还原程度不同。另一方面，在转基因植物中观察到具有抗氧化特性的代谢物水平显著增加，如抗坏血酸、脱氢抗坏血酸、α-生育酚和亚精胺。这些结果表明 CsGolS6 是提高柑橘和其他植物胁迫耐受性的潜在候选基因。
