Tlr0485 is a cAMP-activated c-di-GMP phosphodiesterase in a cyanobacterium Thermosynechococcus

Abstract

Second messenger molecules are crucial components of environmental signaling systems to inte-grate multiple inputs and elicit physiological re-sponses. Among various kinds of second messen-gers, cyclic nucleotides cAMP and cyclic di-GMP (c-di-GMP) play pivotal roles in bacterial environmental responses. However, how these signaling systems are interconnected for a concerted regulation of cellular physiology remains elusive. In a thermophilic cyanobacterium Thermosynechococcus vulcanus strain RKN, inci-dent light color is sensed by cyanobacteriochrome photoreceptors to transduce the light information to the levels of c-di-GMP, which induces cellular aggregation probably via cellulose synthase acti-vation. Herein, we identified that Tlr0485, which is composed of a cGMP-specific phosphodiesterases, adenylate cyclases, and FhlA (GAF) domain and an HD-GYP domain, is a cAMP-activated c-di-GMP phosphodiesterase. We also show biochemical evidence that the two class-III nucleotide cyclases, Cya1 and Cya2, are both ade-nylate cyclases to produce cAMP in T. vulcanus. The prevalence of cAMP-activated c-di-GMP phos-phodiesterase genes in cyanobacterial genomes suggests that the direct crosstalk between cAMP and c-di-GMP signaling systems may be crucial for cyanobacterial environmental responses.