The Upregulated Expression of the Citrus RIN4 Gene in HLB Diseased Citrus Aids Candidatus Liberibacter Asiaticus Infection.

The citrus industry has been threatened by Huanglongbing (HLB) for over a century. Here, an HLB-induced Arabidopsis RPM1-interacting protein 4 ( RIN4 ) homologous gene was cloned from Citrus clementina , and its characteristics and function were analyzed to determine its role during citrus- Candidatus Liberibacter asiaticus ( C Las) interactions. Quantitative real-time PCR showed that RIN4 was expressed in roots, stems, leaves and flowers, with the greatest expression level in leaves. Its expression was suppressed by gibberellic acid, indole-3-acetic acid, salicylic acid and jasmonic acid treatments, but was induced by abscisic acid and salt treatments, as well as wounding. The transient expression of a RIN4-GFP showed that RIN4 was localized in the cell membrane. RIN4 -overexpressing transgenic C. maxima cv. 'Shatianyou' plants were obtained, and some transgenic plants showed greater sensitivity to C Las infection and earlier HLB symptoms appearance than non-transgenic controls. Results obtained in this study indicated that the upregulated expression of RIN4 in HLB diseased citrus may aid C Las infection.