75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

311 Centromeric Retrotransposons: Potential Role of the Integrase C-terminus in Determining
Genomic Distribution
Yi Hou, Xiang Gao, Daniel Voytas
Iowa State University
The plant CR retrotransposons are a highly conserved family of Ty3/gypsy elements found almost exclusively in
centromeric heterochromatin. This biased genomic distribution may be caused by targeted integration of CR retrotransposons
into centromeric regions or by selection against insertions into other chromosomal sites. A variant of the chromodomain
(a chromo-like domain or LCHD) was identified in the C-termini of CR retrotransposon integrases. Chromodomains
recognize specific modifications on histones, and through this recognition, they direct chromodomain-bearing proteins to
specific chromatin domains. We cloned this LCHD and fused it to YFP. In vivo localization experiments showed a specific
sub-nuclear distribution of YFP foci that were coincident with the localization of LPH1, a chromodomain-containing
protein from Arabidopsis. The LCHD foci also overlapped with the centromere-specific protein CENPC. The sub-nuclear
foci became more diffuse in ddm1 mutant leaf cells, which have altered patterns of histone and DNA methylation in
heterochromatin. Our data suggest that the C-termini of CR retrotransposon integrases interact with specific components
of centromeric heterochromatin. We hypothesize that this interaction underlies the novel distribution pattern of the CR
retrotransposon insertions in the genome.
312 A Disrupted MicroRNA Target Site Reveals Novel Regulatory Functions of a Transcription
Factor During Plant Development
Clayton Larue 2 , Jiangqi Wen 1 , John Walker 2
1
The Samuel Roberts Noble Foundation, Ardmore, OK, 2 University of Missouri, Columbia, MO
Regulation of development by microRNA (miRNA)-mediated stability of gene transcripts has become a common
theme in both plants and animals. miRNAs target ~21 nucleotide sites of mRNAs to direct degradation or disrupt their
translation. We identified a semi-dominant mutant, syl for styleless, that shows defects in leaf blade margins, internode
patterning and fruit morphology in an EMS mutagenized Arabidopsis population. A single basepair mutation was found by
map-based cloning in the miRNA target site of a transcription factor, CUC2. This mutation results in an overaccumulation
of transcript in the mutant plant. A mutation in the miRNA corresponding to the mutation in the target site results in a
reversion to a wild-type phenotype. This miRNA target site mutation in an endogenous gene may provide interesting
insights into the roles miRNAs play in plant development.
C.T. Larue and J. Wen contributed equally to this work.