M88体育-明升M88体育讯(通讯员 徐莉清)近日,果蔬园艺作物种质创新与利用全国重点实验室罗正荣教授团队在柿果单宁累积分子调控机制方面取得进展。相关成果以“DkDTX1/MATE1 mediates the accumulation of proanthocyanidin and affects astringency in persimmon”为题在Plant, Cell & Environment在线发表。
我国是柿的原产国,也是栽培历史最悠久,面积最大和产量最多的国家。根据成熟果实在树上能否自然脱涩及其性状遗传特点,现有柿品种分为完全甜柿(简称“甜柿”)和非完全甜柿(简称“涩柿”)。与其他果实不同,柿果肉含有一类特化的单宁细胞,其液泡内含有的大量的可溶性原花青素(俗称“柿单宁”)是导致涩感的主要原因,但甜柿和涩柿的原花青素组成差异较大,其形成机制不明。
M88体育-明升M88体育柿研究团队从中国甜柿中鉴定到与柿单宁转运相关的两个蛋白DkDTX1/MATE1和DkDTX5/MATE5。此前研究发现,DkDTX5/MATE5主要在果实发育中后期表达,其在甜柿果实中的表达量高于涩柿,且偏好性转运儿茶素(C)、表儿茶素(EC)和表儿茶素没食子酸(ECG)等柿单宁前体,Ser-84等位基因变异是其偏好性转运单宁前体的分子基础(Journal of Integrative Plant Biology,2023)。
本研究发现,与DkDTX5/MATE5主要在果实发育的中后期表达有别,DkDTX1/MATE1主要在柿果实发育前期表达,在涩柿的表达量更高。活体叶片和离体果实圆片瞬时转化实验表明,DkDTX1/MATE1过表达不仅显著增加柿单宁含量,还上调相关单宁生物合成基因表达。分子对接、离体转运和定点突变等实验结果表明,DkDTX1/MATE1主要通过68位丝氨酸与柿单宁前体结合,且偏好性转运儿茶素、表儿茶素没食子酸和表没食子儿茶素没食子酸酯(EGCG),与EGCG的结合能力更强。
DkDTX1/MATE1偏好性转运涩柿果实单宁的主要组分,使其积累更多的EGCG,而DkDTX5/MATE5则偏好性转运甜柿果实单宁的主要组分,从而导致甜柿和涩柿单宁累积差异。该研究结果不仅为不同类型柿果单宁组分形成机制的解析提供科学依据,也为涩柿品种的甜柿化遗传改良奠定了基础。
DkDTX/MATE在柿原花青素前体转运中的作用(NA-type 甜柿;A-type 涩柿)
M88体育-明升M88体育果蔬园艺作物种质创新与利用全国重点实验室博士毕业生刘颖为该论文的第一作者,M88体育-明升M88体育柿研究团队的徐莉清高级工程师和张青林副教授为共同通讯作者,陈文兴副教授,罗正荣教授等参与研究。
英文摘要
Proanthocyanidins (PAs) is a kind of polyphenols widely distributed in plants, and their astringent properties can protect plants from herbivores and regulate fruit taste. There is a great difference in PA composition between astringent (A)-type and nonastringent (NA)-type persimmon. Here, we studied the potential of DkDTX1/MATE1 in regulating PAs composition through its preferred transport in persimmon fruit. The results of fluorescence microscope showed that the DkDTX1/MATE1 green fluorescence overlapped with the blue light emitted by PA. Overexpression of DkDTX1/MATE1 in persimmon leaves not only significantly increase the concentrations of PA, but also upregulated the expression of PA biosynthesis pathway genes. Further overexpression of DkDTX1/MATE1 in persimmon fruit discs and stable genetic transformation of DkDTX1/MATE1 also led to PA concentrations increased. Molecular docking and transporter assays showed that DkDTX1/MATE1 preferentially transported catechin, epicatechin gallate and epigallocatechin gallate. DkDTX1/MATE1 mainly bound to the PA precursors via serine at position 68. Our findings indicate that DkDTX1/MATE1 play a role in the accumulation of PAs in early stage of fruit development and affects the astringency of persimmon through preferential transport PA precursors, which provided a theoretical basis for the future use of metabolic engineering to regulate the composition of PAs in persimmon.
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