THE GLK1 ‘REGULON’ ENCODES DISEASE DEFENSE RELATED PROTEINS AND CONFERS RESISTANCE TOFUSARIUM GRAMINEARUMIN ARABIDOPSIS

The maize Golden2-like or GLK genes encode proteins belonging to a class of GARP domain transcriptional activators. GLKs have been observed to be involved in chloroplast development and stress adaptation. In spite of the importance of GLKs in plant processes, thein plantatargets of GLK regulated transcription, however, have not been identified. We use GLK1 overexpression (OE) to study reprogramming of gene expression networks by GLK1 in Arabidopsis and to identify an associated phenotype. GLK1 OE in Arabidopsis confers resistance toFusarium graminearum, a broad host pathogen responsible for major losses in cereal crops. Affymetrix Gene Chip and RT-PCR analyses indicated that GLK1 OE in Arabidopsis reprogrammed gene expression networks to enhance a high constitutive expression of genes encoding proteins involved in basal defences but downregulated genes that are associated with programmed cell death and hypersensitive responses. The nature of the role of GLK1 overexpression in selectively reprogramming defence gene networks could explain its effectiveness in enhancing the development of resistance to the necrotrophic phase ofF. graminearumpathogenesis.