Reduced GDP-l-galactose phosphorylase expression and deficiency of ascorbic acid content lead to decreased fruit set and yield in tomato plants. Reduced GDP-l-galactose phosphorylase expression and deficiency of ascorbic acid content lead to decreased fruit set and yield in tomato plants. GDP-l-galactose phosphorylase (GGP) catalyzes the first step committed to ascorbic acid synthesis. The participation of GDP-l-galactose phosphorylase and ascorbate in tomato fruit production and quality was studied in this work using two SlGGP1 deficient EMS Micro-Tom mutants. The SlGGP1 mutants display decreased concentrations of ascorbate in roots, leaves, flowers, and fruit. The initiation of anthesis is delayed in ggp1 plants but the number of flowers is similar to wild type. The number of fruits is reduced in ggp1 mutants with an increased individual weight. However, the whole fruit biomass accumulation is reduced in both mutant lines. Fruits of the ggp1 plants produce more ethylene and show higher firmness and soluble solids content than the wild type after the breaker stage. Leaf CO2 uptake decreases about 50% in both ggp1 mutants at saturating light conditions; however, O2 production in an enriched CO2 atmosphere is only 19% higher in wild type leaves. Leaf conductance that is largely reduced in both mutants may be the main limitation for photosynthesis. Sink-source assays and hormone concentration were measured to determine restrictions to fruit yield. Manipulation of leaf area/fruit number relationship demonstrates that the number of fruits and not the provision of photoassimilates from the source restricts biomass accumulation in the ggp1 lines. The lower gibberellins concentration measured in the flowers would contribute to the lower fruit set, thus impacting in tomato yield. Taken as a whole these results demonstrate that ascorbate biosynthetic pathway critically participates in tomato development and fruit production.

中文翻译：

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GDP-l-半乳糖磷酸化酶（抗坏血酸合成所需的一种酶）缺乏会降低番茄果实产量

GDP-l-半乳糖磷酸化酶表达降低和抗坏血酸含量缺乏导致番茄坐果和产量下降。GDP-l-半乳糖磷酸化酶表达降低和抗坏血酸含量缺乏导致番茄坐果和产量下降。GDP-l-半乳糖磷酸化酶 (GGP) 催化致力于抗坏血酸合成的第一步。在这项工作中，使用两个 SlGGP1 缺陷型 EMS Micro-Tom 突变体研究了 GDP-l-半乳糖磷酸化酶和抗坏血酸对番茄果实生产和质量的参与。SlGGP1 突变体在根、叶、花和果实中的抗坏血酸浓度降低。ggp1 植物的花期开始延迟，但花数与野生型相似。随着个体重量的增加，ggp1 突变体的果实数量减少。然而，两个突变株系的整个果实生物量积累都减少了。ggp1 植物的果实在破膜期后产生的乙烯更多，硬度和可溶性固形物含量都高于野生型。在饱和光照条件下，两种 ggp1 突变体的叶片 CO2 吸收减少约 50%；然而，在富含二氧化碳的大气中，野生型叶子的氧气产量仅高出 19%。两种突变体中的叶片电导率都大大降低，这可能是光合作用的主要限制。测量汇源测定和激素浓度以确定对果实产量的限制。叶面积/果实数量关系的处理表明果实数量而不是从源头提供的光同化物限制了 ggp1 系中的生物量积累。花中测量的较低赤霉素浓度会导致坐果率降低，从而影响番茄产量。总的来说，这些结果表明抗坏血酸生物合成途径在番茄发育和果实生产中发挥着重要作用。