The Role of Knotted1-Like Homeobox Genes in Shoot Development

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

0131431 Hake Knotted1 is the founding member of the knox (knotted1-like homeobox) gene family that has been identified in all plants surveyed so far. Homeobox genes encode transcription factors that regulate the activities of other genes. Class I knox genes are expressed in the meristem and stem. The initial down-regulation of knox genes in the meristem marks the site of leaf initiation. Ectopic expression of knox genes in leaves due to spontaneous mutations or overexpression results in dramatic alterations in leaf morphology, occasional ectopic meristems and changes in hormone levels. Loss-of-function knox mutants have begun to reveal specific roles for different members. The maize knotted1 (kn1) and Arabidopsis STM genes are required for meristem initiation and/or maintenance, whereas rice osh15 and Arabidopsis KNAT1, also known as brevipedicellus (bp), are required in stem tissues. There are two other class I knox genes in Arabidopsis, KNAT2 and KNAT6. Insertion alleles will be obtained for these two genes. A mosaic analysis of bp will be carried out to determine the role of KNAT1 in different tissues. Genetic analysis will help sort out the roles for different knox genes in Arabidopsis. A number of approaches will be taken to identify targets of the KNOX family that include expression profiling, sequence comparisons and biochemistry. Identification of a large number of potential targets will provide the opportunity to determine which target genes are in common or distinct to different KNOX proteins. A select number of the target genes will be analyzed to determine their function. The long range goal is to understand the role of KNOX proteins in meristem maintenance and plant architecture.