Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

A MAIZE HISTONE DEACETYLASE AND RETINOBLASTOMA-RELATED PROTEIN PHYSICALLY INTERACT AND COOPERATE IN REPRESSING GENE TRANSCRIPTION

LANZANOVA C., LOCATELLI S., ROSSI V., MOTTO M.

Istituto Sperimentale per la Cerealicoltura, sezione di Bergamo, Via Stezzano 24, 24126 Bergamo

isc@spm.it

Rpd3-type histone deacetylases, Retinoblastoma-related proteins, G1/S transition, Zea mays, gene expression

Histone deacetylases (HDACs) play a critical role in eukaryotic gene regulation by altering chromatin structure. In mammalian cells the product of the human retinoblastoma tumor suppressor gene (pRb), a key regulator of cell cycle and differentiation, is one of the transcriptional regulators that can recruit Rpd3-type class I HDACs.

In this study, we investigated whether this mechanism might also be relevant in plants and found both conserved and unique features. The expression patterns and cellular localization of the Zea mays Rpd3-type histone deacetylase (ZmRpd3I) and the retinoblastoma-related (ZmRBR1) homologue were analyzed during maize endosperm development and embryo germination.

Although the expression profile differs for the two proteins, a functional interaction in vivo seems likely. GST pull-down experiments were used to demonstrate the physical interaction between ZmRBR1 and ZmRpd3I proteins. Because ZmRpd3I lacks a LXCXE motif, which is conserved in several pRb interacting proteins, we have mapped the amino acid domains involved in ZmRBR1/ZmRpd3I interaction. Furthermore, we demonstrated that this protein interaction is facilitated by ZmRbAp1, a maize member of the MSI/RbAp family. Co-transformations of tobacco protoplasts with plasmids expressing ZmRBR1 and ZmRpd3I fused to the DNA-binding domain of the tetracycline repressor showed that the two proteins cooperate in actively repressing gene transcription.

Our findings represent the first direct indication that a regulator of important biological processes, ZmRBR1, can recruit histone deacetylase, ZmRpd3I, to control gene transcription in plants.

Differences in the molecular mechanisms of ZmRBR1/ZmRpd3I association between plant and animal systems are discussed.