Gibberellin driven growth inelf3mutantsrequires PIF4 and PIF5

摘要

The regulatory connections between the circadian clock and hormone signaling are essential to understand, as thesetwo regulatory processes work together to time growth processes relative to predictable environmental events.Gibberellins (GAs) are phytohormones that control many growth processes throughout all stages of the plant life cycle,including germination andflowering. An increasing number of examples demonstrate that the circadian clock directlyinfluences GA biosynthesis and signaling. EARLY FLOWERING 3 (ELF3) participates in a tripartite transcriptional complexknown as the Evening Complex (EC). In this capacity, ELF3 is fundamental to core circadian clock activity, as well astime-of-day specific regulation of genes directly responsible for growth control, namely thePHYTOCHROMEINTERACTING FACTOR 4(PIF4) andPIF5genes. Here we show that the GA biosynthesis inhibitor paclobutrazolsubstantially reduces the long hypocotyl and petiole phenotypes of Arabidopsiself3mutants. In addition, loss of ELF3activity causes upregulation of the key GA biosynthesis genesGA20ox1andGA20ox2. Moreover,GA20ox1andGA20ox2expression depends strongly on the redundant activities ofPIF4andPIF5. Thesefindings indicate that the defininggrowth phenotypes ofelf3mutants arisefrom altered GA biosynthesis due to misregulation ofPIF4andPIF5. Theseobservations agree with recent work linking increased GA production with the elongated growth phenotypes of thebarleyelf3mutant. Thus, the role of the EC in regulation of GA biosynthesis and signaling in eudicots is shared withmonocots and, therefore, is a highly conserved mechanism for growth control.