华中农业大学揭示柑橘果实叶绿素和类胡萝卜素代谢的协同调控机制

　　Domesticated citrus varieties are woody perennials and interspecific hybrid crops of global eco nomic and nutritio nal im portance. The citrus fruit ��hesperidium�� is a unique morphological innovation not found in any other plant lineage. Efforts to improve nutritio nal quality of the fruit are predicated on understanding the underlying regulatory mechanisms respo nsible for fruit development, including temporal co ntrol of chlorophyll degradation and carotenoid biosynthesis. Here we investigated the molecular basis of the navel orange （Citrus sinensis� brown flavedo mutation, which co nditions flavedo that is brown instead of orange. To overcome the limitations of using traditio nal genetic approaches in citrus and other woody perennials, we developed a strategy to elucidate the underlying genetic lesion. We used a multi-omics approach to collect data from several genetic sources and plant chimeras, to successfully decipher this mutation. The multi-omics strategy applied here will be valuable in driving future gene discovery efforts in citrus as well as in other woody perennial plants. The comparison of trans criptomic and genomic data from multiple genotypes and plant sectors revealed an underlying lesion in the gene encoding STAY-GREEN protein （SGR）， which simultaneously regulates carotenoid biosynthesis and chlorophyll degradation. However, unlike SGR of other plant species, we found that the carotenoid and chlorophyll regulatory activities could be uncoupled in the case of certain SGR alleles in citrus and thus we propose a model for the molecular mechanism underlying the brown flavedo phenotype. The eco nomic and nutritio nal value of citrus make these findings of wide interest. The strategy implemented, and the results obtained, co nstitute an advance for agro-industry by driving opportunities for citrus crop improvement.

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