Fruit carbohydrate metabolism in an introgression line of tomato with increased fruit soluble solids
Fruit carbohydrate metabolism in an introgression line of tomato with increased fruit soluble solids
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DOI：
10.1093/pcp/pci040
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发表时间：
2005-03-01
影响因子：
4.9
通讯作者：
Sweetlove, LJ
中科院分区：
文献类型：
--
作者：
Baxter, CJ;Carrari, F;Sweetlove, LJ
栽培品种番茄（Lycopersicon esculentum）的一个番茄品系（IL9-2-5）携带了来自野生品种番茄（Lycopersicon pennelli）的9厘米的基因突变，其果实具有高可溶性固结物含量（Brix），这是果实加工品质的重要决定因素。在渐渗段中鉴定出两个与果实可溶性固形物含量有关的数量性状位点（qtl）。其中一个qtl （PW-9-2-5）在本研究中使用的生长条件下是沉默的，而另一个qtl （Brix-9-2-5）编码了一个具有改变动力学性质的果外体转化酶（Lin5）。在这项研究中，我们对渗入系进行了详细的生化分析，试图了解与果实可溶性固结物增加相关的代谢变化。成熟果实中糖度的增加是蔗糖和葡萄糖增加的结果，而天门冬氨酸和丙氨酸的贡献较小。这种基因渗入导致小柱组织中脂质体转化酶活性的显著增加，并在整个果实发育过程中延伸。此外，来自IL9-2-5果实的小柱组织具有更大的吸收外源蔗糖的能力，这一观察结果与渗入的Lin5等位基因的动力学特性一致。除了成熟果糖和一些氨基酸的增加外，代谢产物分析显示，IL9-2-5对果实的代谢几乎没有影响。唯一的其他主要变化是在水果代谢的早期阶段淀粉积累的急剧增加。蔗糖代谢酶或淀粉合成酶的活性没有增加，因此可能是由于蔗糖的可用性增加所致。我们得出结论，导致IL9-2-5中果糖含量增加的主要因素是韧皮部对蔗糖的吸收能力增加。
A tomato line (IL9-2-5) of the cultivated species, Lycopersicon esculentum, carrying a 9 cM introgression from the wild species, Lycopersicon pennelli, produces fruit with high soluble solids content (Brix), an important determinant of fruit quality for processing. Two quantitative trait loci (QTLs) relating to fruit soluble solids content have been identified within the introgressed segment. One of these QTLs (PW-9-2-5) is silent under the growth conditions used in this study, while a second (Brix-9-2-5) has been shown to encode a fruit apoplastic invertase (Lin5) with altered kinetic properties. In this study, we have undertaken a detailed biochemical analysis of the introgression line to attempt to gain an understanding of the metabolic changes associated with increased fruit soluble solids. Increased Brix in ripe fruit was shown to be the result of increased sucrose and glucose, with a more minor contribution from aspartate and alanine. The introgression leads to a pronounced increase in apoplastic invertase activity in the columella tissue that extends throughout fruit development. Furthermore, columella tissue from IL9-2-5 fruit has a greater capacity to take up exogenously supplied sucrose, an observation that is consistent with the kinetic properties of the introgressed Lin5 allele. Apart from the increase in mature fruit sugar and increases in some amino acids, metabolite profiling revealed few other metabolic perturbations in fruit from IL9-2-5. The only other major change was a dramatic increase in starch accumulation at earlier stages of fruit metabolism. This occurred without any increase in the activity of the enzymes of sucrose metabolism or starch synthesis and may therefore be driven by increased availability of sucrose. We conclude that the major factor that leads to increased fruit sugar in IL9-2-5 is an increase in the capacity to take up sucrose unloaded from the phloem.