l-Ascorbate biosynthesis in peach: cloning of six l-galactose pathway-related genes and their expression during peach fruit development
l-Ascorbate biosynthesis in peach: cloning of six l-galactose pathway-related genes and their expression during peach fruit development
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DOI：
10.1111/j.1399-3054.2009.01213.x
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发表时间：
2009-06-01
影响因子：
6.4
通讯作者：
Moriguchi, Takaya
中科院分区：
文献类型：
--
作者：
Imai, Tsuyoshi;Ban, Yusuke;Moriguchi, Takaya
分析了桃果实发育过程中果肉中抗坏血酸（阿萨）含量和6个L-半乳糖途径相关基因的表达。桃果实发育过程中阿萨含量的变化可分为4个时期：阿萨Ⅰ期，盛花后0-36天; AsA Ⅱ期，盛花后37-65天;阿萨Ⅲ期，盛花后66-92天;阿萨Ⅳ期，盛花后93-112天。阿萨III期是阿萨积累的滞后期，但与果实发育的滞后期不一致。T-AsA浓度在早期最高，直到21 DAFB [2-3 μ mol/g鲜重（g（-1）FW）]，并在50和92 DAFB分别降至该值的1/4和1/15。然后T-AsA保持在0.15-0.20 μ mol g（-1）FW，直到在112 DAFB收获。超过90%的T-AsA在21 DAFB之前以还原形式存在。然后还原型阿萨的比例随着阿萨浓度的降低而降低。为明确桃果实阿萨生物合成的主要途径和阿萨的生物合成能力，以未成熟的桃果实（59 DAFB）为材料，研究了几种前体物质对桃果实中AsA合成的影响。阿萨浓度随l-半乳糖酸-1，4-内酯或l-半乳糖（Gal）显著增加，但d-半乳糖醛酸和l-古洛糖酸-1，4-内酯未能增加阿萨，表明Gal途径占主导地位，未成熟桃果肉中阿萨生物合成能力强。在果实发育过程中的Gal途径的最后六个步骤中所涉及的基因的表达进行了测量。研究的基因包括GDP-d-甘露糖焦磷酸化酶（GMPH）、GDP-d-甘露糖-3 '，5'-差向异构酶（GME）、GDP-l-半乳糖鸟苷酰转移酶（GGGT）、l-半乳糖-1-磷酸酶（GPP）、l-半乳糖-1-脱氢酶（GDH）和l-半乳糖酸-1，4-内酯脱氢酶（GLDH）。GMPH、GME和GGGT具有相似的表达模式，在43 DAFB达到峰值。GPP、GDH和GLDH也具有相似的表达模式，在21和91 DAFB时达到两个峰值，尽管GDH的表达相当低。高水平的T-阿萨浓度与果实发育早期（阿萨I）的基因表达水平大致相关，而在其他时期（例如阿萨III和IV）没有这种关系。在此基础上，我们对桃果实中阿萨生物合成的调控进行了讨论。
The l-ascorbate (AsA) content and the expression of six l-galactose pathway-related genes were analyzed in peach flesh during fruit development. Fluctuation of AsA during peach fruit development was divided into four phases based on the overall total AsA (T-AsA) content per fruit: AsA I, 0-36 days after full bloom (DAFB); AsA II, 37-65 DAFB; AsA III, 66-92 DAFB and AsA IV, 93-112 DAFB. Phase AsA III was a lag phase for AsA accumulation, but did not coincide with the lag phase for fruit development. The T-AsA concentration was highest at the early stage until 21 DAFB [2-3 mu mol per gram of fresh weight (g(-1) FW)], and decreased to 1/4 and 1/15 of this value at 50 and 92 DAFB, respectively. T-AsA then remained at 0.15-0.20 mu mol g(-1) FW until harvest at 112 DAFB. More than 90% of the T-AsA was in the reduced form until 21 DAFB. The proportion of reduced form of AsA then decreased concomitantly with the decrease in AsA concentration. To determine the main pathway of AsA biosynthesis and the AsA biosynthetic capacity of peach flesh, several precursors were incubated with immature whole fruit (59 DAFB). The AsA concentration increased markedly with l-galactono-1,4-lactone or l-galactose (Gal), but d-galacturonate and l-gulono-1,4-lactone failed to increase AsA, indicating dominance of the Gal pathway and potent AsA biosynthetic capabilities in immature peach flesh. The expression of genes involved in the last six steps of the Gal pathway was measured during fruit development. The genes studied included GDP-d-mannose pyrophosphorylase (GMPH), GDP- d-mannose-3',5'-epimerase (GME), GDP- l-galactose guanylyltransferase (GGGT), l-galactose-1-phosphate phosphatase (GPP), l-galactose-1-dehydrogenase (GDH) and l-galactono-1,4-lactone dehydrogenase (GLDH). GMPH, GME and GGGT had similar expression patterns that peaked at 43 DAFB. GPP, GDH and GLDH also had similar expression patterns that peaked twice at 21 and 91 DAFB, although the expression of GDH was quite low. High level of T-AsA concentration was roughly correlated with the level of gene expression in the early period of fruit development (AsA I), whereas no such relationships were apparent in the other periods (e.g. AsA III and IV). On the basis of these findings, we discuss the regulation of AsA biosynthesis in peach fruit.