Search

The circadian clock modulates immune responses in plants and animals; however, it is unclear how host-pathogen interactions affect the clock. Here we analyzed clock function in Arabidopsis thaliana mutants with defective immune responses and found that enhanced disease susceptibility 4 (eds4) displays alterations in several circadian rhythms. Mapping by sequencing revealed that EDS4 encodes the ortholog of NUCLEOPORIN 205, a core component of the inner ring of the nuclear pore complex (NPC). Consistent with the idea that the NPC specifically modulates clock function, we found a strong enrichment in core clock genes, as well as an increased nuclear to total mRNA accumulation, among genes that were differentially expressed in eds4 mutants. Interestingly, infection with Pseudomonas syringae in wild-type (WT) plants downregulated the expression of several morning core clock genes as early as 1 h post-infection, including all members of the NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED (LNK) gene family, and this effect was attenuated in eds4. Furthermore, lnk mutants were more susceptible than the WT to P. syringae infection. These results indicate that bacterial infection, acting in part through the NPC, alters core clock gene expression and/or mRNA accumulation in a way that favors bacterial growth and disease susceptibility.

Light signaling pathways interact with the circadian clock to help organisms synchronize physiological and developmental processes to periodic environmental cycles. The plant photoreceptors responsible for clock resetting have been characterized, but signaling components that link the photoreceptors to the clock remain to be identified. Members of the family of NIGHT LIGHT–INDUCIBLE AND CLOCK-REGULATED (LNK) genes play key roles linking light regulation of gene expression to the control of daily and seasonal rhythms in Arabidopsis thaliana. Particularly, LNK1 and LNK2 were shown to control circadian rhythms, photomorphogenic responses, and photoperiod-dependent flowering time. Here we analyze the role of the four members of the LNK family in Arabidopsis in these processes. We found that depletion of the closely related LNK3 and LNK4 in a lnk1;lnk2 mutant background affects circadian rhythms, but not other clock-regulated processes such as flowering time and seedling photomorphogenesis. Nevertheless, plants defective in all LNK genes (lnkQ quadruple mutants) display developmental alterations that lead to increased rosette size, biomass, and enhanced phototropic responses. Our work indicates that members of the LNK family have both distinctive and partially overlapping functions, and are an essential link to orchestrate light-regulated developmental processes.