UV-B调控设施桃光合产物分配与转运的机理

Quality of protected fruit is lower than that of outdoors is a burning and key question in cultivation and breeding. The type, content and scale of soluble sugar was the main determinant for fruit intrinsic quality, which come from photosynthate distribution and translocation. Light quality deterioration caused by greenhouse film absorbing UV-B is one of important environment factors affecting photosynthesis and metabolism during protected culture. Recently, we found that UV-B radiation enrichment benefit to soluble sugar and soluble solids contents in protected peach, however, the regulating mechanism remains ambiguous. In this study, average sugar content nectarine and sugar-high nectarine bred by our laboratory were taken as materials, gradient UV-B radiation were set to interfere photosynthesis and sugar metabolism of peach, then, photosynthetic performance(green peel), photosynthate components, sugar metabolizing enzymes and sucrose transporters(SUTs) expression patterns in peach leaf and fruit were studied, ultrastructure of source-leaf and sink-fruit were observed to dissect reasons of peach fruit sugar accumulation and difference of sugar accumulation between average sugar content nectarine and sugar-high nectarine. Moreover, some signal transduction substances such as G protein, calmodulin(CaM), Ca2+, H+-ATPase may be involved in signal pathway were studied to investigate signal transduction pathway of UV-B regulate sucrose transporters. This study aims to clarify metabolism of UV-B regulate photosynthate allocation and sucrose translocation, which will serve as the foundation for protected fruit sugar accumulation and rational utilization of UV-B.

设施果实品质低于露天是栽培和育种中亟待解决的问题。可溶性糖的种类、含量和比例是果实内在品质的主要决定因素，其积累主要来源于光合产物。设施棚膜吸收UV-B导致的光质变化是影响光合作用及其代谢的重要环境因素之一。本实验室发现，适量增加设施内UV-B辐照有利于提高桃果实的可溶性糖及可溶性固形物含量，但其调控机理尚不清楚。以普通糖度和本实验室新培育出的高糖型油桃为试材，设置梯度UV-B，干涉桃的光合性能和糖代谢过程，研究叶片和果实的光合性能（绿色果皮）、光合产物组分、糖代谢相关酶活性、蔗糖转运蛋白的表达模式和库、源的解剖结构以解析UV-B影响下普通糖度与高糖型果实的糖积累模式及其差异之处。并研究UV-B通过G蛋白、GaM、Ca2+、H+-ATPase等信号转导物质对蔗糖转运蛋白途径的可能调控机制，旨在揭示UV-B调控光合产物分配及蔗糖转运的机理，为设施果实的糖积累及UV-B的合理利用提供理论支撑。

设施果实品质低于露天是生产中亟待解决的关键问题。果实的内在品质主要由可溶性糖的种类、含量和比例决定，其主要来源为光合同化物的分配与转运。设施栽培中，由于棚膜反射、散射及吸收UV-B，导致设施内UV-B不足，改变了光质组成，是影响光合性能及糖代谢的重要因素之一。本项目以前期试验得出的最佳剂量1.44Kj·m−2·d−1为补充剂量，上午9:30-10:30补光1小时。主要研究结果如下：.1. UV-B 辐射可大幅度提高叶绿素b的含量，修复受损的叶绿体，提高净光合速率Pn，但这种修复和提高会随着停止补光而恢复。.2. 叶片中的光合同化物组分主要为蔗糖、山梨醇、葡萄糖和果糖，以山梨醇为主。果实中糖组分主要由蔗糖、葡萄糖和果糖共同组成，蔗糖为主。UV-B辐照可提高果糖、山梨醇和蔗糖含量，激活叶片中蔗糖转运蛋白SUTs的表达，促进蔗糖的跨膜运输，提高源叶-库果的蔗糖转运能力。可见UV-B的补充有利于叶片中的光合产物向果实中转运，从而提高果实含糖量。.3. UV-B处理下桃果实4种主要糖组分在各自代谢通路上的共19条关键基因的定量分析显示，山梨醇代谢的相关基因（S6PDH、NAD-SDH1/2、NADP-SDH和SOT）出现差异表达，蔗糖代谢的相关基因（SUS4、NIV8、SPS3、SUT2、SUT4和 TMT2）变化差异不显著，葡萄糖和果糖代谢通路相关基因中，仅HEX6表现出极显著下调，其它如PFP-β、PFP-α、FLN1、FLN2、FBpase、PFK和HET均表现出显著性差异。表明蔗糖代谢、山梨醇代谢及己糖代谢均不同程度地响应UV-B信号，影响光合同化物的合成和积累。.4. 通过miRNA高通量测序鉴定出15个miRNA响应UV-B处理，其中8个上调，7个下调。对其进行了GO和KEGGpathway分析，结合基因表达情况得出了UV-B调控蔗糖、山梨醇等主要糖组分的作用通路模式图。 .5. UV-B辐照下果实RNA-Seq测序筛选出5个糖代谢相关的DEGs，不同程度地响应UV-B。.6. 叶绿素合成相关基因SCLs所在GRAS转录因子家族在桃中共有48个成员，在叶片、果实和韧皮部中均有表达。多数PpGRAS基因能响应UV-B处理，表明PpGRAS基因家族可能在光响应方面发挥着多种潜在功能。