Submitted to: Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/7/2008
Publication Date: 11/12/2008
Publication URL: www.plantphysiol.org/cgi/content/short/149/1/271
Citation: Meng, Y., Moscou, M., Wise, R.P. 2008. Blufensin1 Negatively Impacts Basal Defense in Response to Barley Powdery Mildew. Plant Physiology. 149(1):271-285. Interpretive Summary: Plant diseases are among the greatest deterrents to crop production worldwide. Pathogenic fungi, viruses, bacteria, insects, and nematodes impact agronomic and horticultural crops, as well as commercial and recreational forests. ARS researchers have isolated a novel regulator of disease defense. The new monocot-specific gene encodes a family of small cysteine-rich peptides, designated blufensins. BLUFENSIN1 (BLN1) is highly induced during infection by pathogenic fungi and contains both structural and sequence similarities to knottins, a diverse family of small disulfide-rich proteins characterized by a unique "disulfide through disulfide knot." This discovery, also supported by the National Science Foundation-Plant Genome Research Program, establishes a previously unrecognized role for small peptides as negative regulators of plant defense. Because common themes govern all plant-pathogen interactions, this finding provides new knowledge of broad significance to plant scientists, and to growers who utilize disease resistance to protect their crops.
Technical Abstract: Plants have evolved complex regulatory mechanisms to control the defense response against microbial attack. Both temporal and spatial gene expression are tightly regulated in response to pathogen ingress, modulating both positive and negative control of defense. BLUFENSIN1 (BLN1), a small peptide belonging to a novel family of proteins in barley (Hordeum vulgare L.), is highly induced by attack from the obligate biotrophic fungus, Blumeria graminis f. sp. hordei (Bgh), causal agent of powdery mildew disease. Computational interrogation of the Bln1 gene family determined that members reside solely in the BEP clade of the Poaceae family, specifically, barley, rice, and wheat. Barley stripe mosaic virus induced gene-silencing (BSMV-VIGS) of Bln1 enhanced plant resistance in compatible interactions, regardless of the presence or absence of functional Mla CC-NBS-LRR alleles, indicating BLN1 can function in an R-gene independent manner. Likewise, transient overexpression of Bln1 significantly increased accessibility towards virulent Bgh. Moreover, silencing in plants harboring the Mlo susceptibility factor decreased accessibility to Bgh, suggesting BLN1 functions in parallel with or upstream of MLO to modulate penetration resistance. Collectively, these data suggest that the grass-specific Bln1 negatively impacts basal defense against Bgh.