赵天永等《Journal of Agricultural and Food Chemistry》2021年
论文题目：ZmAGA1 Hydrolyzes RFOs Late During the Lag Phase of Seed Germination, Shifting Sugar Metabolism Towards Seed Germination Over Seed Aging Tolerance
论文作者：Yumin Zhang, Dan Li, Lynnette M. A. Dirk, A. Bruce Downie, and Tianyong Zhao*
论文摘要：Raffinose family oligosaccharides (RFOs) are accumulated during the late stage of seed development and hydrolyzed during seed germination. The process of raffinose hydrolysis during seed germination and how this process affects seed vigor remains unknown. We report here that maize alkaline α-galactosidase 1 (ZmAGA1) protein is translationally induced and is capable of hydrolyzing RFOs as well as a precursor, galactinol, during seed germination. Constitutively overexpressing ZmAGA 1 in Arabidopsis decreased both RFOs and galactinol contents of mature, desiccated, and 30 hours after imbibition (HAI) seeds, yet enhanced the seed germination percentage under either salt or somewhat osmotic-stress conditions at earlier times during the time course. However, ZmAGA 1 overexpression also decreased the seed aging tolerance of mature, desiccated seeds as compared with wild type (WT) or those overexpressing GFP . Compared to that of WT control seeds, the atsip 2 (mutant of Arabidopsis AtSIP 2 (seed imbibition protein 2, encoding alkaline α-galactosidase)) seeds have similar RFOs and galactinol contents in mature, desiccated seeds but significantly increased the amount of these metabolites at 30 HAI. This retention of RFOs and galactinol in atsip 2 results in seeds that exhibit lowered seed germination percentage under either salt or osmotic stress conditions, and yet, increased seed aging tolerance relative to WT. Similarly, when maize seeds were imbibed in the presence of a specific α-galactosidase inhibitor (1-deoxygalactonojirimycin) as compared to those imbibed in water, greater amounts of raffinose and galactinol were detected; the seeds exhibited decreased seed germination percentages but increased seed aging tolerance. Taken together, these data suggest that both maize seed germination and seed aging tolerance can be simultaneously regulated through careful temporal manipulation of ZmAGA 1 expression.
玉米种子萌发过程中 ZmAGA1 基因的表达受到翻译水平的调控。组成型过量表达 ZmAGA1 促进了棉子糖的水解，提高了种子的萌发速度，但降低了种子的耐储性。在玉米种子引发过程中添加碱性半乳糖苷酶抑制剂可以维持种子引发过程中棉子糖含量，显著提高种子引发后的种子耐储藏能力。作者建议通过组成型表达棉子糖合成酶基因，诱导表达棉子糖水解酶基因 ZmAGA1 既可以提高种子中棉子糖含量，提高玉米种子的耐储性，又可以在种子萌发过程中提高棉子糖的水解能力，提高玉米种子的萌发速度。