Analysis of regulatory mechanisms of C/N-balance by plastid signaling using sugar-sensitive mutants

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We recently identified an Arabidopsis gain-of-function mutant of plastidic invertase (INV-E), sicy-192, as a sucrose sensitive mutant, and found that INV-E participates in regulating the carbon/nitrogen (C/N) balance. Interestingly, PGE was suppressed in the mutants on treatment with sucrose, suggesting that INV-E regulates C/N balance via the plastid signaling. We created and analyzed double mutants of sicy-192 and genome uncoupled 1 (gun1-101), which lacks GUN1, a master regulator of the plastid signaling. On treatment with sucrose, the expression of photosynthesis- and nitrogen assimilation-related genes was lower and higher, respectively, in the sicy-192 mutants compared to the wild-type plants. Interestingly, the perturbation of C/N balance was recovered by the disruption of GUN1, suggesting an involvement of INV-E in the GUN1-mediated plastid signaling.