Global analysis of gene expression during development and ripening of citrus fruit flesh.: A proposed mechanism for citric acid utilization
Global analysis of gene expression during development and ripening of citrus fruit flesh.: A proposed mechanism for citric acid utilization
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DOI：
10.1007/s11103-006-9037-7
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发表时间：
2006-11-01
影响因子：
5.1
通讯作者：
Talon, Manuel
中科院分区：
文献类型：
--
作者：
Cercos, Manuel;Soler, Guillermo;Talon, Manuel
利用基因芯片技术研究了非气候性自交不亲和柑橘（Citrus clementina）果肉发育和成熟过程中7000个基因的表达变化。数据表明，2243个推定的unigenes显示出显着的表达变化。功能分类显示，编码调控蛋白的基因在上调的基因簇中显著过量表达。转录组学研究以及对选定代谢物的分析突出了柑橘果实发育和成熟过程中发生的关键生理过程，如水分积累、碳水化合物积累、酸减少、色素取代（类胡萝卜素积累和叶绿素减少）和抗坏血酸减少。通常，综合分析强烈表明特定代谢替代品的流行。这一观察结果已举例说明了柠檬酸盐利用机制的建议，在柑橘业的一个非常重要的过程。通过实时RT-PCR验证的微阵列数据表明，柠檬酸盐依次代谢为异柠檬酸，2-酮戊二酸和谷氨酸。此后，谷氨酸既用于谷氨酰胺生产，又通过γ-氨基丁酸（GABA）分流（GABA ->琥珀酸半醛->琥珀酸）分解。最后一个观察结果似乎具有特殊的相关性，因为它将质子消耗反应谷氨酸+ H+ -> GABA + CO2与高酸水平联系起来。GG-MS测定结果表明，谷氨酸是恒定的，而GABA水平下降，在成熟的协议与可行的激活GABA分流在酸catalysis。这一建议提供了一个令人信服的解释柠檬酸和细胞质酸度的强烈减少，发生在柑橘果肉发育和成熟过程中。
Microarrays of cDNA have been used to examine expression changes of 7000 genes during development and ripening of the fruit flesh of self-incompatible Citrus clementina, a non-climateric species. The data indicated that 2243 putative unigenes showed significant expression changes. Functional classification revealed that genes encoding for regulatory proteins were significantly overrepresented in the up-regulated gene clusters. The transcriptomic study together with the analyses of selected metabolites highlighted key physiological processes occurring during citrus fruit development and ripening such as water accumulation, carbohydrate build-up, acid reduction, pigment substitutions (carotenoid accumulation and chlorophyll decreases) and ascorbic acid diminution. Often, the combined analyses strongly suggested prevalence of specific metabolic alternatives. This observation has been exemplified with the proposal for a mechanism for citrate utilization, a process of much importance in citrus industry. Microarray data validated by real-time RT-PCR suggested that citrate was sequentially metabolyzed to isocitrate, 2-oxoglutarate and glutamate. Thereafter, glutamate was both utilized for glutamine production and catabolyzed through the gamma-aminobutirate (GABA) shunt (GABA -> succinate semialdehyde -> succinate). This last observation appears to be of special relevance since it links the proton consuming reaction glutamate + H+ -> GABA + CO2 with high acid levels. GG-MS determinations showed that glutamate was constant while GABA levels decreased at ripening in agreement with a feasible activation of the GABA shunt during acid catabolism. This suggestion provides a convincing explanation for the strong reduction of both citrate and cytoplasmatic acidity that takes place in citrus fruit flesh during development and ripening.