Study On MAPK-WRKY Module Regulates Plastid Retrograde Signaling

Plastid retrograde signaling is essential for coordinating the expression of plastid and photosynthesis-associated nuclear genes(PhANGs).The chloroplast protein GUN1 integrates three plastid signaling pathways,but how signals are transduced from plastid to the nucleus is mostly unclear.In this study,using molecular genetics and biochemistry approaches,we found that components recruited from the families of MAP kinases(MAPK)and WRKY transcription factors were involved in signaling downstream of GUN1.Besides,RNA blot analysis indicates that MAPKKK18-MKK(7/9/10)-MPK(14/16)-WRKY(30/41)negatively regulates the expression of the nuclear marker gene LHCBs,suggesting that the MAPK-WRKY module is involved in suppressing PhANG expression in response to plastid retrograde signals.Compare to gun1 mutant,double mutants of mapkkk18 gun1,mkk10 gun1,mpk14 gun1 and wrky41 gun1 showed similar gun phenotypes,while oeWRKY30 gun1 and oeWRKY41 gun1 displayed decreased gun phenotype,implying that MAPK-WRKY module is involved in regulating GUN1-depenent retrograde signaling.In addition,Yeast two-hybrid experiments showed that MPK14 directly regulates the function of WRKY30.All these results provide a new perspective for the study of plastid retrograde signaling.