Role of tomato BRANCHED1 -like genes in the control of shoot branching

MARTÍN-TRILLO MAR; GONZÁLEZ-GRANDÍO, EDUARDO;; SERRA, F; MARCEL, FABIEN; RODRÍGUEZ-BUEY, MARÍA LUISA; SCHMITZ, GREGOR; THERES; KLAUS; BENDAHMANE, ABDEL; DOPAZO, HERNAN; CUBAS, PILAR

PLANT JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 p. 1 - 14

0960-7412

In angiosperms, shoot branching greatly determines overall plant architecture and affects fundamental aspects of plant life. Branching patterns are determined by genetic pathways widely conserved across angiosperms. In Arabidopsis thaliana (Brassicaceae,Rosidae) BRANCHED1 (BRC1) plays a central role in this process, acting locally to arrest axillary bud growth. In tomato (Solanum lycopersicum, Solanaceae, Asteridae)we have identified two BRC1-like paralogs, SlBRC1a and SlBRC1b. These genes are expressed in arrested axillary buds and both are down-regulated upon bud activation,although SlBRC1a is transcribed at much lower levels than SlBRC1b. Alternative splicing of SlBRC1a renders two transcripts encoding two BRC1-like proteins with different C-t domains due to a 3´-terminal frameshift. The phenotype of loss-of-function lines suggests that SlBRC1b has retained the ancestral role of BRC1 in shoot branch suppression while SlBRC1a does not seem to have a major role in this process. We have isolated the BRC1a and BRC1b genes of other Solanum species and have studied their evolution rates across the lineages. These studies indicate that after duplication of an ancestral BRC1-like gene, BRC1b genes continued evolving under a strong purifying selection, consistent with the conserved function of SlBRC1b in shoot branching control. In contrast, the coding sequences of Solanum BRC1a genes have evolved at a higher evolution rate. Branch-site tests indicate that this does not reflect relaxation but rather positive selective pressure for adaptation.