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

Abstract

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 (CLas) 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 CLas 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 CLas infection.

Insights into the Molecular Basis of Huanglongbing Tolerance in Persian Lime (Citrus latifolia Tan.) through a Transcriptomic Approach

“…The RPM1 gene has been reported as being upregulated in susceptible citrus genotypes [37], which could be associated with the upregulated expression of the RIN4 gene [45] as these genes have shown to have a positive regulatory interaction [46]. Recently, it was demonstrated that the overexpression of RIN4 aids in the establishment of the CLas infection and the development of HLB symptoms [47].…”