Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2000
Publication Date: N/A
Interpretive Summary: Fungal diseases of cereals destroy grain quality by inhibiting seed development and depositing toxins on seeds. Cereal seeds contain potent antifungal proteins called permatins. However, these occur within the seed and thus are not available to prevent fungal colonization of the floral leaves surrounding the seed. One approach to develop barley and oats with stronger resistance to fungi is to clone and analyze permatin and other antifungal protein genes and determine when and where these genes are activated. This knowledge may allow us to produce permatin proteins in the right tissues and at the right time to deter fungal colonization. In this study, permatin genes of oat and barley were cloned. The genes are mainly expressed in developing seeds at the time of pollination and when seeds develop to the doughy stage. The genes are expressed at low levels in vegetative tissues, including the floral leaves. The complete lack of expression in stems may allow fungi an unchallenged infection route through the plant. Permatin gene activity increases modestly after infection with Fusarium head blight (scab) fungus. These studies will provide potential DNA markers to aid in the breeding of fungus-resistant barley and oats. This will benefit the cereal foods industry, growers, the malting and brewing industries, and consumers by providing safer foods.
Technical Abstract: Permatins are antifungal thaumatin-like proteins (TLPs) of the PR-5 family of pathogenesis-related proteins. Permatins occur in many cereals, but little is known of their expression and roles. Permatin cDNA clones were produced and used to study expression in developing barley and oat seeds. Actin and CDC48 mRNAs declined rapidly following inoculation of barley spikes with Fusarium graminearum. Despite this, permatin mRNA levels increased. Studies of permatin gene expression in healthy plants revealed that developing barley and oat seeds accumulate permatin mRNA in an unusual bimodal pattern. Permatin mRNA and protein are highly abundant around the time of pollination and then decrease rapidly to near-zero. A second peak occurs in the doughy stage of development. Antibody and DNA probe hybridization studies showed that expression initially occurs in the ovary wall and then switches to the aleurone and ventral furrow of developing seeds, reaching a peak in the doughy stage. Small amounts of permatin mRNAs also occur in certain vegetative tissues. The barley and oat permatin sequences provided sufficient comparisons between cereal TLPs to suggest that deletions or additions in specific elements could have led to the divergence of leaf- and seed-specific TLPs.