<scp>OsAUX</scp>1 controls lateral root initiation in rice (<scp><i>O</i></scp><i>ryza sativa</i> <scp>L</scp>.)

Abstract

Abstract Polar auxin transport, mediated by influx and efflux transporters, controls many aspects of plant growth and development. The auxin influx carriers in A rabidopsis have been shown to control lateral root development and gravitropism, but little is known about these proteins in rice. This paper reports on the functional characterization of OsAUX 1 . Three OsAUX 1 T ‐ DNA insertion mutants and RNAi knockdown transgenic plants reduced lateral root initiation compared with wild‐type ( WT ) plants. OsAUX 1 overexpression plants exhibited increased lateral root initiation and OsAUX 1 was highly expressed in lateral roots and lateral root primordia. Similarly, the auxin reporter, DR 5‐ GUS , was expressed at lower levels in osaux 1 than in the WT plants, which indicated that the auxin levels in the mutant roots had decreased. Exogenous 1‐naphthylacetic acid ( NAA ) treatment rescued the defective phenotype in osaux 1‐1 plants, whereas indole‐3‐acetic acid ( IAA ) and 2,4‐ D could not, which suggested that OsAUX 1 was a putative auxin influx carrier. The transcript levels of several auxin signalling genes and cell cycle genes significantly declined in osaux 1 , hinting that the regulatory role of OsAUX 1 may be mediated by auxin signalling and cell cycle genes. Overall, our results indicated that OsAUX 1 was involved in polar auxin transport and functioned to control auxin‐mediated lateral root initiation in rice.