Tomato photorespiratory glycolate‐oxidase‐derived H2O2 production contributes to basal defence against <italic>Pseudomonas syringae</italic>.

Abstract: Despite being essential for C₃ plants, photorespiration is believed to cause a significant crop yield loss even under future climates. However, how photorespiration affects plant basal defence still remains largely unknown. Here, we studied the involvement of photorespiration in tomato–<italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> DC3000 interaction focusing on three photorespiratory genes. Inoculation with <italic>P. syringae</italic> increased photorespiration rate (Pr) and expression of glycolate oxidase (<italic>GOX2</italic>), serine glyoxylate aminotransferase (<italic>SGT</italic>) and serine hydroxyl methyltransferase (<italic>SHMT1</italic>); however, inhibition of photorespiration by isonicotinic acid hydrazide decreased tomato basal defence against <italic>P. syringae</italic>. Furthermore, silencing of <italic>GOX2</italic>, <italic>SGT</italic> or <italic>SHMT1</italic> genes in tomato decreased Pr but increased susceptibility to <italic>P. syringae</italic>, whereas transient overexpression of <italic>GOX2</italic>, <italic>SGT</italic> or <italic>SHMT1</italic> in tobacco increased basal defence. Further study revealed that salicylic acid (SA) signalling is involved in <italic>GOX2</italic>‐mediated, <italic>SGT</italic>‐mediated and <italic>SHMT1</italic>‐mediated defence. Moreover, H₂O₂ pretreatment remarkably alleviated the <italic>GOX2</italic> silencing‐induced depression in basal defence and SA signalling, whereas it had no effect on that of <italic>SGT</italic>‐silenced and <italic>SHMT1</italic>‐silenced plants. Taken together, these results suggest that H₂O₂ is critical for <italic>GOX2</italic>‐modulated but not <italic>SGT</italic>‐modulated or <italic>SHMT1</italic>‐modulated SA signalling and subsequent basal defence against <italic>P. syringae</italic>. This work deepens the understanding of photorespiration‐involved defence responses to bacterial attack in plants. [ABSTRACT FROM AUTHOR]