Poster: Vegetative Development

Abs # 449: Functional analysis of KNOX genes from the moss Physcomitrella patens.

Presenter:	Champagne, Connie EM, cechampagne@ucdavis.edu
Authors	Champagne, Connie EM (A)   Sinha, Neelima R (A)
Affiliations:	(A): University of California, Davis

Homeobox genes determine cell fate by acting as transcriptional regulators of collections of developmental genes. KNOTTED1-LIKE homeobox (KNOX) genes can be subdivided into two classes based on sequence similarities and expression patterns (Bharathan et al. (1999) Mol. Biol. Evol. 16:553-563). Higher plant Class 1 KNOX genes regulate the formation and maintenance of meristematic tissue, while the function of Class 2 genes remains to be determined (Long et al. (1996) Nature 379:66-69; Serikawa et al. (1996) Plant Mol. Biol. 32:673-683). It has been postulated that factors such as the change in expression of KNOX genes have played a role in the evolution of plant leaf morphology and that Class 1 KNOX genes may have had a role in the acquisition of leaves in the earliest vascular land plants (Sinha et al. (1993) Genes Dev. 7:787-795). Three independent genes named MKN1-3, MKN2 and MKN4 were cloned from a P. patens genomic library. Phylogenetic analysis indicates that MKN2 and MKN4 are Class 1 genes, and MKN1-3 is a Class 2 gene. MKN2 is expressed in chloronemal apical cells. The expression patterns of MKN1-3 and MKN4 are similar. Expression of both genes was observed in some, but not all, chloronemal apical and sub-apical cells. Often, the signal was not homogenous in all cells, indicating that MKN1-3 and MKN4 RNA are sub-cellularly localized. Using directed gene knockout, the function of MKN2, MKN4 and MKN1-3 have been disrupted. Knockout phenotypes will be described. Deducing the function of moss KNOX genes may illuminate how the transition to three dimensional growth, characteristic of the Embryophytes, occurred.