Candidatus Liberibacter asiaticus (CLas)-mediated volatile emissions and salicylic acid-jasmonic acid antagonism alter Asian citrus psyllid behavior in navel orange

Citrus huanglongbing arises primarily due to Candidatus Liberibacter asiaticus ( C Las), transmitted by Asian citrus psyllids (ACP). To investigate the defense mechanisms of citrus against ACP feeding mediated by C Las, we investigated the metabolomic and transcriptomic variations in navel orange subjected to feeding by either ACP C Las-infected (ACP+) or -noninfected (ACP−) Asian citrus psyllids. This resulted in the establishment of the following groups: ACP+24 h, ACP+72 h, ACP−24 h, ACP−72 h, and control groups, respectively. The results indicated that both C Las and ACP influenced the release of volatile organic compounds, flavonoid biosynthesis, salicylic acid (SA)-jasmonic acid (JA) signaling pathway, and photosynthesis in citrus. Specifically, the levels of 3-carene, linalool, methyl salicylate, and citronellol were increased at ACP+24 h, exhibiting attraction effect on ACP−, while acting as a repellent to ACP+, which may promote the spread of C Las. Genes CsDXS3, CsADH, and CsADH3 probably contributed to in geraniol degradation. SA signaling was activated, upregulating the genes of nonexpressor of pathogenesis-related and pathogenesis-related proteins in systemic acquired resistance. However, downregulation of CsAOS , CsAOC , CsJAR1 , and CsJAZ corresponded with decreasing trend in compounds related to α-linolenic acid metabolic, indicating the SA-JA antagonism. These findings offer novel insights into C Las involvement in citrus initial responses to ACP feeding, contributing to understanding of citrus- C Las-ACP interactions.