Gene expression profile of arabidopsis plants that overexpress ZEITLUPE/LOV KELCH PROTEIN1: Up-regulation of auxin-inducible genes in hypocotyls

Abstract

ZEITLUPE (ZTL) is a blue-light photoreceptor with an F-box motif in Arabidopsis thaliana. The molecular mechanisms underlying the ZTL-dependent control of the circadian rhythm and repression of photoperiodic flowering are relatively well characterized. ZTL also positively regulates hypocotyl elongation under light, but the molecular mechanisms remain unknown. Using microarray analysis, we showed that 194 genes, including 17 SMALL AUXIN UP RNA (SAUR) genes (SAUR9, 15, 16, 19, 20, 22–24, 28, 29, 61–67) and two AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) genes (IAA7, 29), were up-regulated and 283 genes were down-regulated in ZTL-overexpressing Arabidopsis seedlings. The results were confirmed for SAUR22, 23, and IAA29 by real-time quantitative reverse-transcription PCR. Application of the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA), the auxin antagonist α-(phenyl ethyl-2-one)-indole-3-acetic acid (PEO-IAA), or the auxin biosynthesis inhibitor 5-(4-chlorophenyl)-4H-1,2,4-triazole-3-thiol (YUCASIN) inhibited hypocotyl elongation enhanced in ZTL-overexpressing seedlings. Our data suggest the involvement of auxin and auxin-inducible genes, including SAURs and IAAs, in hypocotyl elongation in ZTL-overexpressing seedlings.