Dormancy and reactivation of the seed and its microbiome: a holobiont perspective

Desiccation-tolerant seeds provide an intriguing system for studying microbial dormancy, which includes reversible inactivation and reactivation in response to stress. Focusing on bacterial responses to desiccation and rehydration, we offer a holistic interpretation of dormancy and quiescence within the seed holobiont, highlighting both parallels and distinctions between microbes and their plant host. Based on pilot evidence, we propose that microbial dormancy supports persistence throughout the life cycle of desiccation-tolerant seeds. Transcriptomic analyses of seed-transmitted bacteria have identified genes implicated in inactivation and the viable-but-nonculturable state. Our analysis of Xanthomonas citri pv. fuscans illustrates this during seed maturation. However, the signals triggering microbial reactivation and the potential reciprocal interactions between seed dormancy and quiescence, and microbial dormancy, remain unknown. Elucidating this interplay within the seed holobiont could enhance plant growth and health either by promoting seed germination through microbial inoculation or by enabling early detection of seed-transmitted phytopathogens.