植物ABCG转运蛋白功能的研究进展

Advances in understanding the functions of plant ABCG transporters

高等植物中细胞器及细胞之间是由生物膜分隔开来,但在植物的生理代谢及应对逆境胁迫的过程中,细胞器及细胞之间需要大量的信号与物质的交流.多数情况下,这些跨膜交流由膜上的转运蛋白来执行,其中以ABCG亚家族为代表的ABC转运蛋白家族是一类介导多种不同类型物质的跨膜转运以完成相应功能的转运蛋白.植物比其他真核生物拥有数量更多的ABCG转运蛋白,表明植物中ABCG转运蛋白具有多样且重要的功能. ABCG转运蛋白不仅参与植物正常生长发育过程中许多物质的转运,执行诸多重要的生理功能,还广泛参与植物对干旱、重金属、温度、渗透和抗生素等非生物胁迫,以及病原菌、害虫和植物化感作用造成的生物胁迫响应过程中的信号与物质转运,说明ABCG既与植物的正常生长发育相关,也在植物抵抗逆境胁迫中发挥重要作用.本文对植物ABCG转运蛋白的结构、分类、生理功能及在抗生物与非生物逆境胁迫的功能进行系统总结,为深入了解植物ABCG转运蛋白多样化功能、研究趋势和利用植物分子育种技术对ABCG基因进行表达调控以获得具有优良特性的植物新种质提供重要借鉴和参考.

Biomembranes serve as barriers that separate organelles and cells. Despite the divisions, a significant number of signalsand substrates must be transported across biomembranes during plant metabolism and responses to various abiotic andbiotic stresses. In plants, transmembrane transportations are mostly facilitated by two main types of transporters: Carrierproteins and channel proteins. Among these transporters, the ATP binding cassette (ABC) transporter family, a large andmultifunctional group, plays a crucial role in mediating the transmembrane transportation of diverse substances. The ABCtransporter family can be further grouped into eight subfamilies: ABCA to ABCG and ABCI. Notably, the ABCGsubfamily stands out as the largest, and displays heightened higher functional diversity in the ABC transporter family. Inplants, only two types of ABCG transporters have been identified: The full-size pleiotropic drug resistance (PDR)transporters and the half-size white-brown complex (WBC) transporters. PDR transporters are equipped with twonucleotide-binding domains (NBDs) and two transmembrane domains (TMDs), and can independently carry out substratetransportation. Conversely, WBC transporters possess only a single NBD and TMD, requiring the formation ofhomodimers or heterodimers for substrate transportation. There is a greater abundance of ABCG transporters as comparedto other eukaryotes, suggesting their diverse range of important roles in plant biology. Indeed, many studies have shownthat plant ABCG transporters play key roles in many aspects of plant development, including stomata opening, hormonetransportation (e.g., cytokinin, abscisic acid, jasmonic acid, and strigolactones), sporopollenin transport, cuticle synthesisprecursor exportation, and transportation of secondary metabolites such as tonquinol, ginsenosides, β-caryophyllene, andcapsaicin. Furthermore, plant ABCG transporters are widely involved in plant responses to abiotic stresses such as heavymetal (e.g. aluminum, cadmium, copper, and lanthanum) resistance by facilitating efflux of heavy metals, droughtresistance, osmotic stress, and high-temperature resistance through abscisic acid transportation and formation of thickercuticle. They are also known to regulate abscisic acid transportation, cuticle thickness, as well as kanamycin resistancethrough antibiotic sequestration into the vacuole of plant cell. Plant ABCG transporters are known to play roles in bioticresistance against pathogens and pests by regulating jasmonic acid, salicylic acid, and anti-pathogen metabolitestransportation and accumulation. They play roles in allelopathy by mediating chemical compound secretion into theenvironment. This review presents a comprehensive discussion of recent progress in the structures, classifications,physiological functions, and roles of plant ABCG transporters. Current research advances highlight the crucial roles ofABCG transporters not only in plant growth and development but also in plant resistance to diverse abiotic and bioticstresses. We conclude by proposing five important research trends for future studies on ABCG transporters andhighlighting the potential use of plant molecular breeding technology to generate new plant germplasm with enhancedcharacteristics by regulating the expression of ABCG transporter genes.