Abiotic Stress Resistance Analysis of Lilium pumilum Overexpressing the LpMT2 Gene

Plant metallothioneins (MT) are cysteine-rich proteins present in plants that can improve a plant’s salt tolerance. Therefore, a greater understanding of the MT gene in lily (Lilium pumilum), Liliaceae, is an important factor in the development and cultivation of improved salt-tolerant varieties and enriching plant resources for saline soils. A type 2 MT gene (GenBank access number: MH319787, designated as LpMT2) was isolated from L. pumilum leaves. The response mechanism to stress was then investigated, which provided the basis for molecular breeding of L. pumilum for stress tolerance. The LpMT2 gene amino acid sequence is highly homologous to that of type 2 MT protein. Quantitative real-time PCR (qPCR) determined that different plant tissues expressed the LpMT2 gene differently and these expressions were dependent on the specific stress. Transgenic plants with LpMT2 gene exhibited significantly increased resistance to salt and oxidative stress compared with untransgenic plants. The LpMT2 transgenic plants had better growth, greater chlorophyll and proline content, less malondialdehyde (MDA) content and cell membrane permeability, greater superoxide dismutase (SOD) activity, less Na+ content, greater K+ content and Na+ efflux, and less K+ efflux. These results determined that the transformed LpMT2 gene in L. pumilium plays an important role in enhancing the plant’s salt tolerance and antioxidant capacity.