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DEVELOPMENT AND HORMONE ACTION

An AGAMOUS-Related MADS-Box Gene, XAL1 (AGL12), Regulates Root Meristem Cell Proliferation and Flowering Transition in Arabidopsis^1,[W],[OA]

Laboratorio de Genética Molecular, Desarrollo y Evolución de Plantas, Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad Universitaria, México D.F. 04510, Mexico (R.T.-L., B.G.-P., A.G.-A., R.V.P.-R., S.-H.K., F.A., E.R.A.-B.); Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México (J.G.D.); and ICREA and LGMV (Institució Catalana de Recerca i Estudis Avançats y Laboratori de Genética Molecular Vegetal, CSIC-IRTA), IBMB-CSIC C, 08034 Barcelona, Spain (S.P.)

MADS-box genes are key components of the networks that control the transition to flowering and flower development, but their role in vegetative development is poorly understood. This article shows that the sister gene of the AGAMOUS (AG) clade, AGL12, has an important role in root development as well as in flowering transition. We isolated three mutant alleles for AGL12, which is renamed here as XAANTAL1 (XAL1): Two alleles, xal1-1 and xal1-2, are in Columbia ecotype and xal1-3 is in Landsberg erecta ecotype. All alleles have a short-root phenotype with a smaller meristem, lower rate of cell production, and abnormal root apical meristem organization. Interestingly, we also encountered a significantly longer cell cycle in the strongest xal1 alleles with respect to wild-type plants. Expression analyses confirmed the presence of XAL1 transcripts in roots, particularly in the phloem. Moreover, XAL1::β-glucuronidase expression was specifically up-regulated by auxins in this tissue. In addition, mRNA in situ hybridization showed that XAL1 transcripts were also found in leaves and floral meristems of wild-type plants. This expression correlates with the late-flowering phenotypes of the xal1 mutants grown under long days. Transcript expression analysis suggests that XAL1 is an upstream regulator of SOC, FLOWERING LOCUS T, and LFY. We propose that XAL1 may have similar roles in both root and aerial meristems that could explain the xal1 late-flowering phenotype.

² These authors contributed equally to the article.

³ Present address: Department of Environmental Horticulture, University of Seoul, 90 jeonnong-dong, Dongdaemun-gu, Seoul 130–743, Korea.

⁴ Present address: Comisión Nacional para el Uso y Conocimiento de la Biodiversidad, Liga Periférico-Insurgentes Sur 4903, Col. Parques del Pedregal, Tlalpan, CP.14010 Mexico D.F., Mexico.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Elena R. Alvarez-Buylla (eabuylla{at}gmail.com).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.108647

^* Corresponding author; e-mail eabuylla{at}gmail.com.

Received September 3, 2007; accepted January 11, 2008; published January 18, 2008.