5-氨基乙酰丙酸(ALA),作为一种新型的植物生长调节剂,是所有生物体中卟啉化合物生物合成的关键前体。许多研究报道外源ALA处理可以改善水果的甜度。然而,ALA促进水果中糖含量增加的机制尚不清楚。在这项研究中,我们发现ALA显著促进桃果实蔗糖积累和SPS(蔗糖磷酸合成酶)活性。ALA治疗后14、28、42、50和60天,果实蔗糖含量提高了23%,43%,37%,40%和16%,分别,与对照治疗相比,SPS酶活性提高了21%,28%,47%,37%和29%,分别。相关分析表明,ALA处理下桃果实蔗糖含量与SPS活性呈极显著正相关。随后,生物信息学用于鉴定桃果中SPS基因家族成员,结果发现PPSPS基因家族有四个成员,分布在1号、7号和8号染色体上,分别命名为PpSPS1、PpSPS2、PpSPS3和PpSPS4。qRT-PCR结果表明,在果实发育过程中,PpSPS2和PpSPS3响应ALA高表达,PpSPS2的表达与桃果实SPS活性和蔗糖积累呈正相关。烟草亚细胞定位结果表明,PpSPS2主要分布在细胞质和细胞核中,而PpSPS3主要分布在细胞核中。本研究结果将为进一步研究ALA在桃果实发育成熟过程中PPSPS的功能及对糖代谢的调控奠定基础。
5-Aminolevulinic acid (ALA), as a novel plant growth regulator, is a critical precursor for the biosynthesis of porphyrin compounds in all organisms. Many studies have reported that exogenous ALA treatment could improve fruit sweetness. However, the mechanism by which ALA promotes the increase in sugar content in fruit remains unclear. In this study, we found that ALA significantly promoted sucrose accumulation and SPS (sucrose phosphate synthase) activity in peach fruit. At 14, 28, 42, 50 and 60 days after ALA treatment, sucrose content of fruit was increased by 23%, 43%, 37%, 40% and 16%, respectively, compared with control treatment, and SPS enzyme activity was increased by 21%, 28%, 47%, 37% and 29%, respectively. Correlation analysis showed that the sucrose content of peach fruit under ALA treatment was significantly positively correlated with SPS activity. Subsequently, bioinformatics was used to identify SPS gene family members in peach fruit, and it was found that there were four members of the PpSPS gene family, distributed on chromosomes 1, 7 and 8, named PpSPS1, PpSPS2, PpSPS3 and PpSPS4, respectively. The results of qRT-PCR showed that PpSPS2 and PpSPS3 were highly expressed in response to ALA during fruit development, and the expression of PpSPS2 was positively correlated with SPS activity and sucrose accumulation in peach fruit. The results of tobacco subcellular localization showed that PpSPS2 was mainly distributed in the cytoplasm and nucleus, while PpSPS3 was mainly distributed in the nucleus. The results of this study will lay the foundation for further study on the functions of PpSPS and the regulation of sugar metabolism during the development and ripening of peach fruit by ALA.