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ARS Home » Pacific West Area » Albany, California » Plant Gene Expression Center » Research » Publications at this Location » Publication #182076
Title: AUXIN RESPONSE FACTOR 2 (ARF2): A PLEIOTROPIC DEVELOPMENTAL REGULATOR

Author
item OKUSHIMA, YOKO - ARS-UCB PLNT GENE EXP CTR
item MITINA, IRINA - ARS-UCB PLNT GENE EXP CTR
item QUACH, HONG - ARS-UCB PLNT GENE EXP CTR
item Theologis, Athanasios

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2005
Publication Date: 7/1/2005
Citation: Okushima, Y., Mitina, I., Quach, H.L., Theologis, A. 2005. AUXIN RESPONSE FACTOR 2 (ARF2): a pleiotropic developmental regulator. Plant Journal. 43(1):29-46.

Interpretive Summary: The plant hormone auxin regulates ethylene production in plants by enhancing the transcription of ACC synthase (ACS) genes. ACS is the key enzyme in ethylene biosynthesis. The auxin signaling pathway responsible for the enhancement of ACS activity is mediated by the Aux/IAA-ARF system of transcription factors. We have used reverse genetics for identifying auxin responsive factors (ARF) responsible for auxin-regulated ACS synthase activity. We discovered that ARF2, a member of the ARF family of transcription factors, regulates ACS activity and by extension ethylene production. Mutant Arabidopsis plants for ARF2 are resistant to senescence. The prospect arises that inactivation of the same type of gene in agronomically important crops retard senescence.

Technical Abstract: AUXIN RESPONSE FACTORS (ARFs) regulate auxin-mediated transcriptional activation/repression. They are encoded by a gene family in Arabidopsis, and each member is thought to play a central role in various auxin-mediated developmental processes. We have characterized three arf2 mutant alleles, arf2-6, arf2-7 and arf2-8. The mutants exhibit pleiotropic developmental phenotypes, including large, dark green rosette leaves, delayed flowering, thick and long inflorescence, abnormal flower morphology and sterility in early formed flowers, large organ size and delayed senescence and abscission, compared with wild-type plants. In addition, arf2 mutant seedlings have elongated hypocotyls with enlarged cotyledons under various light conditions. The transcription of ACS2, ACS6 and ACS8 genes is impaired in the developing siliques of arf2-6. The phenotypes of all three alleles are similar to those of the loss-of-function mutants obtained by RNA interference or co-suppression. There is no significant effect of the mutation on global auxin-regulated gene expression in young seedlings, suggesting that ARF2 does not participate in auxin signaling at that particular developmental stage of the plant life cycle. Because ARF2 is thought to function as a transcriptional repressor, the prospect arises that its pleiotropic effects may be mediated by negatively modulating the transcription of downstream genes in signaling pathways that are involved in cell growth and senescence.