AnAGAMOUS-Related MADS-Box Gene,XAL1(AGL12), Regulates Root Meristem Cell Proliferation and Flowering Transition in Arabidopsis

Rosalinda Tapia-LóPez,Francisca Acevedo,Adriana Garay-Arroyo,Rigoberto V PéRez-RuíZ,Sun-Hyung Kim,Soraya Pelaz,Elena R Alvarez-Buylla,Berenice GarcíA-Ponce,Joseph G Dubrovsky

doi:10.1104/pp.107.108647

Rosalinda Tapia-LóPez, Francisca Acevedo + Show 7 more

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https://doi.org/10.1104/pp.107.108647

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Abstract

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, XAL1beta-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.

Highlights

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
Sequence analysis of XAL1 indicated that this gene is a member of the MADS-box transcription factor family (Fig. 1A) and recent phylogenetic analyses suggested that XAL1 is sister to the rest of the AG-related genes (Martınez-Castilla and Alvarez-Buylla, 2003; Parenicovaet al., 2003)
reverse transcription (RT)-PCR detected low expression of XAL1 in the xal1-1 allele, which correlates with its intermediate phenotype, whereas the other two alleles had no expression of XAL1 mRNA (Fig. 1C)

Summary

Introduction

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. MRNA in situ hybridization showed that XAL1 transcripts were found in leaves and floral meristems of wildtype plants This expression correlates with the late-flowering phenotypes of the xal mutants grown under long days. Normal morphogenesis depends on the equilibrium between cell proliferation and differentiation (i.e. cellular homeostasis), whereas transcriptional regulatory networks reliably translate genetic information to yield specific and complex multicellular patterning In both animals and plants, elegant models of pattern formation have suggested the existence of mechanisms that determine developmental identities in precise manners (Coen and Meyerowitz, 1991; Lawrence and Morata, 1994). The MADS-box gene family encodes a large variety of transcriptional regulators of plant and animal development (Messenguy and Dubois, 2003). Plant type I is closely related to the animal SRF factors, whereas plant type II is more similar to the MEF type of animals in their MADS domains than to

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