Abstract
Lateral roots of Arabidopsis temporarily grow obliquely relative to the gravity vector after the initiation and then grow downward. We searched for genes controlling growth direction of lateral roots by analyzing mutant hy5. In hy5 lateral roots, transition from oblique to downward growth is retarded. Because ABA treatments promoted the transition in hy5, we examined T-DNA insertion lines of ABA-inducible genes and found that lateral roots of rd29a showed retarded transition. Because RD29A expression at root tips of lateral roots was decreased in hy5, RD29A might function in transition from oblique to downward growth in lateral roots. Microarray analyses were conducted in hy5 and wild-type root tips of primary and lateral roots which were classified into 3 growth stages according to their growth direction and length. According to statistical significance and availability of T-DNA insertion lines we chose candidate genes whose expression was correlated to growth direction irrespective of genotype. Of 28 mutants examined, several showed more retarded or forwarded transition of growth direction in lateral roots.
