Coordinated regulation of the mitochondrial retrograde response by circadian clock regulators and ANAC017

Mitochondrial retrograde signaling(MRS)supports photosynthetic function under a variety of conditions.Induction of mitochondrial dysfunction with myxothiazol(a specific inhibitor of the mitochondrial bc1 complex)or antimycin A(an inhibitor of the mitochondrial bc1 complex and cyclic electron transport in the chloroplast under light conditions)in the light and dark revealed diurnal control of MRS.This was evidenced by(1)significantly enhanced binding of ANAC017 to promoters in the light compared with the dark in Arabidopsis plants treated with myxothiazol(but not antimycin A),(2)overlap in the experimentally determined binding sites for ANAC017 and circadian clock regulators in the promoters of ANAC013 and AOX1a,(3)a diurnal expression pattern for ANAC017 and transcription factors it regulates,(4)altered expression of ANAC017-regulated genes in circadian clock mutants with and without myxothiazol treatment,and(5)a decrease in the magnitude of LHY and CCA1 expression in an ANAC017-overexpressing line and protein–protein interaction between ANAC017 and PIF4.This study also shows a large difference in transcriptome responses to antimycin A and myxothiazol in the dark:these responses are ANAC017 independent,observed in shoots and roots,similar to biotic challenge and salicylic acid responses,and involve ERF and ZAT transcription factors.This suggests that antimycin A treatment stimulates a second MRS pathway that is mediated or converges with salicylic acid signaling and provides a merging point with chloroplast retrograde signaling.

Unique and conserved features of floral evocation in legumes

Legumes, with their unique ability to fix atmo- spheric nitrogen, play a vital role in ensuring future food security and mitigating the effects of climate change because they use less fossil energy and produce less greenhouse gases compared with N-fertilized systems. Grain legumes are second only to cereal crops as a source of human and animal food, and they contribute approximately one third of the protein consumed by the human population. The productivityof seed crops, such as grain legumes, is dependent on flowering. Despite the genetic variation and importance of flowering in legume production, studies of the molecular pathways that control flowering in legumes are limited. Recent advances in genomics have revealed that legume flowering pathways are divergent from those of such model species as Arabidopsis thaliana. Here, we discuss the current understanding of flowering time regulation in legumes and highlight the unique and conserved features of floral evocation in legumes.