AGO1 DEFINES A NOVEL LOCUS OF ARABIDOPSIS CONTROLLING LEAF DEVELOPMENT

An allelic series of the novel argonaute mutant (ago1-1 to ago1-6) of the herbaceous plant Arabidopsis thaliana has been isolated, The ago1 mutation pleotropically affects general plant architecture, The apical shoot meristem generates rosette leaves and a single stem, but axilla ry meristems rarely develop, Rosette leaves lack a leaf blade but stil l show adaxial/abaxial differentiation, Instead of cauline leaves, fil amentous structures without adaxial/abaxial differentiation develop al ong the stem and an abnormal inflorescence bearing infertile flowers w ith filamentous organs is produced, Two independent T-DNA insertions i nto the AGO1 locus led to the isolation of two corresponding genomic s equences as well as a complete cDNA. The AGO1 locus was mapped close t o the marker mi291a on chromosome 1. Antisense expression of the cDNA resulted in a partial mutant phenotype, Sense expression caused some t ransgenic lines to develop goblet-like leaves and petals, The cDNA enc odes a putative 115 kDa protein with sequence similarity tea translati on products of a novel gene family present in nematodes as,yell as hum ans, No specific function has been assigned to these genes, Similar pr oteins are not encoded by the genomes of yeast or bacteria, suggesting that AGOI belongs to a novel class of genes with a function specific to multicellular organisms.