Temperature dependent RNA metabolism in Xylella fastidiosa during cold stress and grapevine infection
Reoccurrence of Pierce’s disease of grapes, caused by Xylella fastidiosa, is known to be influenced by environmental factors, particularly cold temperatures during overwintering. Grapevines in colder regions are often cured of X. fastidiosa infection over the winter season, depending on cultivar, time of inoculation, and disease severity. The dynamics of X. fastidiosa low temperature adaption and survival during persistent infections in planta is still poorly understood. RNA metabolism is an essential part of bacterial response to low temperature, including inducible expression of RNA binding proteins, helicases, and exoribonucleases. Characterization of two X. fastidiosa RNA-binding family cold shock protein (CSP) homologs revealed that neither was cold-inducible at the transcriptional or post-transcriptional level, suggesting a diminished cold adaptation response in this pathogen. However, expression of X. fastidiosa cold response RNA helicase, srmB, is reduced in a CSP mutant (Δcsp1) compared with wild type X. fastidiosa, indicating a potential regulatory role of Csp1 in RNA metabolism during temperature response. Understanding the cold-adaptation process of X. fastidiosa is important as it relates to the ability of this pathogen to survive through the winter in infected plants depending on geographic location and climatic conditions.