Molecular cloning of a root hairless gene rth1 in rice

Root hairs, projections from the epidermal cells of the roots, are contributing to water and nutrient uptake and anchorage to the soil. To better understand genetic control of root hair formation in rice, we analyzed root hairless 1 (rth1) mutant that was induced by NaN3 treatment. SEM observation showed that in rth1 plants, root hair elongation was abolished after the formation of bulge. High-resolution mapping using 2,088 segregants revealed three predicted genes in a 38-kb candidate interval on chromosome 7. Sequences comparison of the three genes between wild-type Oochikara and rth1 detected a nucleotide substitution only in apyrase (OsAPY). This nucleotide substitution (G → A) lies in the junction between the third intron and the forth exon, and results in the splicing anomaly to the rth1 cDNA sequence. Transgenic plants with introduced OsAPY allele restored normal root hairs and plant growth, showing a complementation of rth1 phenotype. We concluded that the root hairless phenotype of rth1 is caused by a mutation of OsAPY. OsAPY appears to be an important gene for root hair elongation and plant growth in rice.