INDUCTION OF MESSENGER-RNA ACCUMULATION CORRESPONDING TO A GENE ENCODING A CELL-WALL HYDROXYPROLINE-RICH GLYCOPROTEIN BY FUNGAL ELICITORS

The Hrgp (hydroxyproline-rich,glycoprotein) gene codes in maize for on e of the most abundant proteins of the cell wall. HRGPs may contribute to the structural support of the wall and they have also been involve d in plant defense mechanisms. This second aspect has been tested for the Hrgp gene in maize where, in contrast with the situation in dicot species, the gene is encoded by a single-copy sequence. Hrgp mRNA accu mulation is induced in maize suspension-cultured cells by elicitors, i solated either from maize pathogenic or non-pathogenic fungi. The indu ction of Hrgp mRNA accumulation by elicitor extracted from Fusarium mo niliforme has been studied in detail. The level of induction depends o n elicitor concentration and remains high until at least 24 h. Ethylen e and protein phosphorylation appear to be involved in the transductio n pathway of Hrgp gene activation by the F. moniliforme elicitor but n ot by 5 mu M methyl jasmonate or 1 mM salycilic acid. Different compou nds known to participate in plant stress responses such as ascorbic ac id or reduced glutathione have also a positive effect on Hrgp mRNA acc umulation.