Characterisation of polycomb-group genes from Antirrhinum majus and Arabidopsis thaliana

• Main Author: Wilson, Carol Jane
• Published: University of Edinburgh 2001
• Subjects: 581.35
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663874

The <i>CURLY LEAF (CLF) </i>gene, which shows homology with the <i>Drosophila </i>Pc-G gene <i>Enhancer of zeste (E(z))</i>, also regulates the expression of homeotic genes. In higher plants three classes of floral homeotic function exist, which act combinatorially to specify the identity of the four concentric whorls of the flower. <i>CLF</i> is required to repress the <i>c</i> function homeotic gene <i>AGAMOUS (AG)</i> in leaves, inflorescence stems and in outer floral whorls. Unlike the animal Pc-G genes, which act on many targets, the <i>Arabidopsis CLF</i> gene acts mainly on <i>AG.</i> To test whether <i>CLF</i> homologues have a similar function in other plants, or have other targets, <i>CLF</i> homologues were isolated and characterised from <i>Antirrhinum majus</i>, a distant relative of <i>Arabidopsis. </i>Two genes were identified and named <i>ANTIRRHINUM CURLY LEAF 1 </i>and <i>2 (ANTCLF1 </i>and <i>2)</i>; both encode proteins that show greater similarity to CLF than any other plant Pc-G protein on databases. Because ANTCLF1 and 2 were more similar to one another than to CLF, it is likely that the genes arose from a recent gene duplication. Both genes are expressed within the meristem and primordia of vegetative and floral tissue consistent with a role during both vegetative and floral development. The strong similarity in sequence and expression suggests that the two genes may be functionally redundant. To determine their biological function, forward and reverse genetic screens were conducted to identify mutations that disrupt the genes, these proved unsuccessful. Pc-G genes are thought to repress their targets in a heritable fashion. To investigate whether the <i>Arabidopsis </i>Pc-G gene <i>CLF</i> is required persistently to maintain <i>AG </i>repression, its time of action was investigated. A transgenic line with steroid inducible CLF+ activity was used to determine the development time of CLF silencing.