PLASTID ISOPRENOID BIOSYNTHESIS
The plastid-localized methylerythritol phosphate (MEP) pathway synthesizes the isoprenoid precursors of essential photosynthesisrelated compounds and hormones. Flores-Pérez et al. (pages 1303–1315) report on the Arabidopsis mutant rif1 (resistant to inhibition by FSM), which has a lesion in a GTPase homolog required for ribosome assembly and plastid protein synthesis. As shown on the cover, the rif1 mutant grows in the presence of the MEP pathway inhibitor fosmidomycin, which causes a developmental block and severe albino phenotype in the wild type. The authors show that the mutant has increased levels of the first two enzymes of the MEP pathway, resulting from their decreased degradation in mutant plastids, and that the stromal Clp protease complex is involved in this process. The results suggest that plastidial isoprenoid biosynthesis is finely adjusted by regulating the degradation of MEP pathway enzymes.
PC:华中农大解析一个ABA功能模块调控柑橘胡萝卜素合成的机制
胡萝卜素的合成与果实成熟过程中的ABA信号密切相关。本研究发现柑橘果实成熟过程中两个参与ABA信号转导的转录因子CsERF110 and CsERF53可以通过诱导胡萝卜素合成基因(CsGGPPS, CsPSY, CsPDS, CsCRTISO, CsLCYB2, CsLCYE, CsHYD, CsZEP, and CsNCED2)的表达来促进胡萝卜素的合成。
分析显示CsERF110一方面可以直接诱导 CsERF53的表达，另一方面二者可以在蛋白水平上互作以 CsERF110-CsERF53复合物的形式发挥作用.
小结：本研究解析了 ABA信号途径中的CsERF110-CsERF53复合物调控柑橘胡萝卜素合成的机制。
Model for the positive feedback regulatory loop between ABA and carotenoid metabolisms mediated by the transcriptional regulatory module CsERF110-CsERF53 in citrus. CsERF110 responds to ABA signaling and activates the expression of multiple carotenogenic genes (CsGGPPS, CsPSY, CsPDS, CsCRTISO, CsLCYB2, CsLCYE, CsHYD, and CsNCED2) to promote carotenoid accumulation. Meanwhile, CsERF53 is not only induced by ABA signaling, but also directly activated by ERF110, which in turn activates the expression of several carotenogenic genes (CsGGPPS, CsPSY, CsHYD, and CsNCED2), and ultimately promoted carotenoid biosynthesis. Furthermore, CsERF110 interacts with CsERF53, and their interaction further enhances their activation of downstream carotenogenic genes. In turn, ABA as ripening signal significantly induces the regulation and interaction of CsERF110 and CsERF53 in feedback regulation, thereby promoting carotenoid biosynthesis and fruit coloration. In general, there is a positive feedback regulation loop between the CsERF110-CsERF53 regulatory module and the ABA signaling, which determines citrus carotenoid biosynthesis.
原文：An abscisic acid-responsive transcriptional regulatory module CsERF110-CsERF53 orchestrates citrus fruit coloration
