Anti-IRX1 (aa 424-479) polyclonal antibody

Because of genetic heterogeneity present in idiopathic scoliosis, we previously defined clinical subsets (a priori) from a sample of families with idiopathic scoliosis to find genes involved with spinal curvature. Previous genome-wide linkage analysis of seven families with at least two individuals with kyphoscoliosis found linkage (P-value=0.002) in a 3.5-Mb region on 5p13.3 containing only three known genes, IRX1, IRX2, and IRX4. In this study, the exons of IRX1, IRX2, and IRX4, the conserved noncoding elements in the region, and the exons of a nonprotein coding RNA, LOC285577, were sequenced. No functional sequence variants were identified. An intrafamilial test of association found several associated noncoding single nucleotide variants. The strongest association was with rs12517904 (P=0.00004), located 6.5kb downstream from IRX1. In one family, the genotypes of nine variants differed from the reference allele in all individuals with kyphoscoliosis, and two of three individuals with scoliosis, but did not differ from the reference allele in all other genotyped individuals. One of these variants, rs117273909, was located in a conserved noncoding region that functions as an enhancer in mice. To test whether the variant allele at rs117273909 had an effect on enhancer activity, zebrafish transgenesis was performed with overlapping fragments of 198 and 687bp containing either the wild type or the variant allele. Our data suggests that this region acts as a regulatory element; however, its size and target gene(s) need to be identified to determine its role in idiopathic scoliosis.

Cellulose is synthesized by cellulose synthases (CESAs) contained in plasma membrane-localized complexes. In Arabidopsis thaliana, three types of CESA subunits (CESA4/IRREGULAR XYLEM5 [IRX5], CESA7/IRX3, and CESA8/IRX1) are required for secondary cell wall formation. We report that mutations in these proteins conferred enhanced resistance to the soil-borne bacterium Ralstonia solanacearum and the necrotrophic fungus Plectosphaerella cucumerina. By contrast, susceptibility to these pathogens was not altered in cell wall mutants of primary wall CESA subunits (CESA1, CESA3/ISOXABEN RESISTANT1 [IXR1], and CESA6/IXR2) or POWDERY MILDEW-RESISTANT5 (PMR5) and PMR6 genes. Double mutants indicated that irx-mediated resistance was independent of salicylic acid, ethylene, and jasmonate signaling. Comparative transcriptomic analyses identified a set of common irx upregulated genes, including a number of abscisic acid (ABA)-responsive, defense-related genes encoding antibiotic peptides and enzymes involved in the synthesis and activation of antimicrobial secondary metabolites. These data as well as the increased susceptibility of ABA mutants (abi1-1, abi2-1, and aba1-6) to R. solanacearum support a direct role of ABA in resistance to this pathogen. Our results also indicate that alteration of secondary cell wall integrity by inhibiting cellulose synthesis leads to specific activation of novel defense pathways that contribute to the generation of an antimicrobial-enriched environment hostile to pathogens.