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

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 5.18

MADS-BOX GENES CONTROLLING THE FLORAL TRANSITION IN RICE

KATER M.M.*, FORNARA F.**, PELUCCHI N.**, MONTI G.**, GREGIS V.**, COLOMBO L.**

*) Dipartimento di Genetica e Biologia dei Microrganismi

**) Dipartimento di Biologia, Università di Milano, Via Celoria 26, 20133 Milano, Italy

MADS-box transcription factor, protein interactions, flowering, rice

In plants MADS-box genes are involved in various steps of vegetative and reproductive development. In particular, their role is essential in the regulation of the floral transition and in the determination of identity of the inflorescence, and floral meristems and flower organs.

Recently, we have isolated three rice MADS-box genes putatively involved in the transition to flowering: OsMADS18, OsMADS22, OsMADS47. Phylogenetic analysis places OsMADS18 in the SQUA sub-family, closely linked to AP1 and FUL from Arabidopsis. The predicted OsMADS18 amino acid sequence is also highly homologous to PFG, a Petunia gene which promotes flowering. OsMADS22 and OsMADS47 belong to the StMADS11 clade together with SHORT VEGETATIVE PHASE (SVP) from Arabidopsis, a MADS-box gene involved in flowering repression.

In situ expression analysis showed that OsMADS18 and OsMADS22 transcripts can be detected in all plant tissues at different developmental stages and in particular in meristematic tissues. As revealed by northern blot analysis, OsMADS47 expression is restricted to leaves.

We have started with a transgenic approach to study the function of these genes by overexpression and by down-regulation using RNAinterference. Transgenic rice plants in which OsMADS18 was overexpressed have been obtained and analysed. These plants show a reduction in growth and flower earlier in respect to wild-type plants. Expression analysis showed that OsMADS47 is down-regulated in OsMADS18 overexpressing plants. Based on these data together with protein-protein interaction data a working-model to explain the involvement of MADS-box factors in the floral transition will be discussed.