ABSTRACT
The objective was to investigate the expression of a lipid transfer protein gene (LTP) both in bromegrass (Bromus inermis) cells and seedlings after exposure to abiotic stresses, abscisic acid (ABA), anisomycin, and sphingosine. A full-length cDNA clone BG-14 isolated from bromegrass suspension cell culture encodes a polypeptide of 124 amino acids with typical LTP characteristics, such as a conserved arrangement of cysteine residues. During active stages of cold acclimation LTP expression was up-regulated, whereas at the final stage of cold acclimation LTP transcript level declined to pre-acclimation level. A severe drought stress induced the LTP gene; yet, LTP expression doubled 3 d after re-hydration. Both temperature and heat shock duration influence LTP induction; however temperature is the primary factor. Treatment with NaCl stimulated accumulation of LTP mRNA within 15 min and the transcripts remained at elevated levels for the duration of the salinity stress. Most interestingly, Northern blots showed LTP was rapidly induced not only by ABA, but also by anisomycin and sphingosine in suspension cell cultures. Of the three chemicals, ABA induced the most rapid and highest response in LTP expression as well as highest freezing tolerance, whereas sphingosine was the least active for both LTP expression and freezing tolerance.
