The effects of ‘Candidatus Liberibacter asiaticus’ infection on the protein expression profiles and nutrient status of citrus plants

Abstract

Huanglongbing (HLB) is a lethal disease of citrus and the bacterium, ‘Ca. Liberibacter asiaticus’ (Las) is the most prevalent etiological agent of the disease worldwide. Here, proteomic analyses via 2‐DE and mass spectrometry were employed to elucidate the protein expression profiles in leaves of Las‐infected greenhouse‐grown citrus grapefruit and lemon plants that are pre‐symptomatic or symptomatic for HLB. We also applied ICP spectroscopy to identify the effect of the disease on the nutrient status of greenhouse‐grown citrus grapefruit, lemon, and trifoliate plants. 2‐DE analysis revealed over 200 and 70 protein spots in grapefruit and lemon leaves, respectively, that were differentially expressed due to Las infection compared to uninfected plants. Interestingly, LC‐MS analysis showed that chitinase and starch synthase are among a subset of proteins precociously induced in the leaves of Las‐infected grapefruit and lemon plants. Furthermore, nutrient status analysis of leaves suggests that active accumulations of Zn and Ca in lemon and trifoliate plants, respectively, are associated with citrus response to Las infection. In summary, our results provide novel insights into potential host‐specific response mechanisms associated with HLB, which is important for early detection and better nutritional management of the disease. This project was supported by the USDA, Agricultural Research Service.