A stress-responsive multifunctional protein involved in .BETA.-oxidation in tobacco plants

Biotic and abiotic-induced wounding is one of the severest stresses that plants suffer throughout the growing period. Upon injury, plants rapidly activates a set of genes, which encode diverse proteins to cope with damages. Screening such genes that were transcriptionally activated within 30 min after mechanical wounding in tobacco plants, we identified a particular clone encoding a multfunctional protein, and designated as NtMFP (Nicotiana tabacum multifunctional protein). The deduced polypeptide is constituted of 668 amino acids with an apparent molecular mass of 72.3 kDa, and bacterially expressed protein exhibited a clear b-oxidation activity. Fusion proteins with GFP were observed in cytosol, when expressed in onion epidermal cell layers. In addition to wounding, NtMFP transcripts were induced by tobacco mosaic virus infection, and by jasmonic acid treatments. When NtMFP was suppressed by the RNAi, transgenic tobacco showed dwarfism, early senescence and reduced expresstion of jasmonic acid-responsive genes. Multifunctional protein is generally considered to catalyze multiple steps of the fatty acid b-oxidation. It is also proposed to be involved in the b-oxidation step of jasmonic acid biosynthesis. The present results suggest the possibility that NtMFP commonly functions not only in fatty acid catabolism but also in jasmonic acid biosynthesis pathway.