Submitted to: Isozymes International Congress Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/6/1998
Publication Date: N/A
Technical Abstract: In response to destruction of barley and wheat crops by the head scab fungus, Fusarium graminearum, we have cloned genes which encode antifungal proteins of the seed. We are attempting to express these genes in floral organs which surround the seed to intercept and inhibit fungal growth before mycotoxin can be produced. Antifungal thaumatin-like proteins (TLPs) of seeds, permatins, occur in many cereals. Permatins are 21-24 kDa PR-5 pathogenesis-related proteins. Zeamatin from maize was the first permatin purified. Its ability to permeate and lyse fungal hyphae suggested the term "permatin". Zeamatin's 3-D structure has been determined to be essentially identical to that of thaumatin. Permatin cDNA clones, pBARPERM1 and 2, were produced from developing barley seed mRNA, and pOATPERM1 was produced from oat seed mRNA. Sequence comparisons suggested that deletions in two specific sequences were involved in the evolution of the (smaller) leaf TLPs. Developing barley and oat seeds accumulate permatin (and oat globulin) mRNA in an unusual bimodal pattern. Peak mRNA levels occur very early, followed by sudden decreases to near-zero levels and a second peak in the doughy stage of seed development. Barperm1 mRNA is confined to tissues surrounding the starchy endosperm. Oatperm1 mRNA is distributed between the endosperm and surrounding tissues. Small amounts of permatin mRNAs occur in vegetative tissues, except the stem. We have produced barley transformed with OATPERM1 and an antisense construct of BARPERM1. Tests are underway to determine whether the former resist Fusarium.