Characterization of an Oxidative Stress Inducible Nonspecific Lipid Transfer Protein Coding cDNA and its Promoter from Drought Tolerant Plant Prosopis juliflora

Abiotic stress is the principal cause of crop failure worldwide. Prosopis juliflora is a hardy plant reported to be tolerant to drought, salinity, extremes of soil pH, and heavy metal stress. Here, we report the characterization of a cDNA clone for a putative nonspecific lipid transfer protein (Pj LTP1) found abundantly in a drought stressed leaf cDNA library of P. juliflora and its promoter. A multiple sequence analysis of Pj LTP1 with well-established and officially designated nonspecific lipid transfer proteins allergens revealed high similarity at the amino acid level. Northern analysis of Pj LTP1 in P. juliflora leaves under oxidative stress revealed steady upregulation at the time points analyzed. A 929-bp fragment was isolated from the 5' end of Pj LTP1, and transient reporter gene expression studies revealed it to be a functional promoter. Several cis-acting elements previously reported to function in stress response were found in this promoter. The possible reasons for changes in gene expression during stress in relation to the host plant's stress tolerance mechanisms are discussed.