REV Gene Family and Meristem Initiation

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

0131492 Clark All above ground post-embryonic development in Arabidopsis occurs through the initiation of organs at shoot and flower meristems. Thus, the initiation of shoot and flower meristems is a fundamental prerequisite for subsequent pattern formation and cell differentiation. The role of the REVOLUTA (REV) gene in the initiation of lateral shoot and flower meristems has recently been described. Genetic and molecular analysis suggested that REV acts early in the process of lateral meristem initiation, and is required, at least indirectly, for the reactivation of known meristem regulators, such as the CLV loci, WUS and STM, at lateral positions. REV encodes a type III HD-zip protein, containing a putative DNA-binding homeodomain, a leucine zipper domain likely involved in dimerization, and a START sterol/lipid binding domain. Other analysis has revealed that REV is also required for normal vascular organ development. Consistent with these developmental roles, REV is expressed early in vascular tissue, organs and lateral meristems. REV is a member of a closely related gene family consisting of five genes in Arabidopsis. The variable expressivity of rev mutant phenotypes and the lack of phenotypes for loss-of-function alleles of other gene family members suggest that these genes may exhibit functional redundancy. Indeed, other gene family members have been implicated in organ development/polarity and vascular development through the analysis of gain-of-function alleles. Functional redundancy is likely to be very common among plant genomes, where the level of gene duplication is significantly higher than among animal genomes. However, little is known about the nature of functional specification among an entire gene family that has evolved multiple developmental roles. The REV gene family thus makes an excellent system in which to determine the relationships between the various gene family members and the potentially overlapping roles that each plays in plant development. This proposal seeks to use the REV gene family to characterize a functionally interrelated gene family, as well as advance understanding of lateral meristem development. Loss-of-function alleles have been identified for each family members and genetic analysis will determine to which development processes each gene contributes. The mRNA expression patterns of each gene will be assessed, as well as the functional equivalence of the proteins encoded by each gene. Potential downstream targets will be characterized. This work will provide a critical comprehensive understanding of the relationships, and perhaps origins, of a functionally interrelated gene family. This will be of significance to other plant developmental systems in which the action of redundant genes are important. Furthermore, the roles of key regulators of lateral meristem initiation will be characterized.