Ectopic Overexpression of Lectin in Transgenic Brassica juncea Plants Exhibit Resistance to Fungal Phytopathogen and Showed Alleviation to Salt and Drought Stress

Abstract

Lectins are ubiquitous in nature and one of the most important secondary metabolites in plants. They are heterogeneous class of proteins that bind specifically and reversibly to carbohydrates and are used as a defence tool against various abiotic and biotic stresses. In this study, we describe generation of transgenic Brassica juncea plants over-expressing chickpea lectin in conferring fungal resistance. In addition, the transgenic plants also showed resistance against salinity (NaCl) and mannitol induced drought stress. The stable integration and transcript expression of the transgene was confirmed by southern blot and RT-PCR analysis in the transgenic plants. The transgenic lines were evaluated for resistance against Alternaria brassicae as assessed by the number and size of lesions and time taken for leaf necrosis, the Alternaria infection was delayed and restricted in the transgenic plants with the protection varying from 36-60% in different transgenic lines compared to the Untransformed Control (UC) plants. In addition, the transgenic Brassica juncea plants also showed tolerance against high salinity and drought stress. The Expression of lectin gene imparts greater water retention capacity, higher proline content and more chlorophyll retention with less membrane damage and reduction in electrolyte leakage in the transgenic plants compared to UC plants. Together, these findings suggest the potential use of chickpea lectin gene to engineer the crop plants for broad spectrum biotic and abiotic stress tolerance to improve crop productivity.