Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

The Use Of Genomic Approach To Identify Factors Involved In The Induction Of Flower Bud Differentiation In Citrus

Ravit Goldberg-Moeller , Lyudmila Shlizerman , Naftali Zur , Etti Or , Avi Sadka

  The Department of Fruit Trees Sciences, ARO, The Volcani Center, P.O. Box 6 Bet Dagan 50250, Israel

The induction of flower bud differentiation in Citrus occurs during the fall and early winter. Gibberellins applied during this period inhibit flowering, while inhibitors of gibberellins biosynthesis induce flowering. In contrast to Citrus, in Arabidopsis, gibberellins induce bolting. Previous works in Citrus strongly suggest that genes controlling flowering in Arabidopsis, such as Leafy, Apetala1 and TFL, may act in a similar manner also in Citrus. This research is aimed at identifying genes which play a role in the induction of flower bud differentiation, especially in regards to the action of gibberellins. Trees of ‘Or’ mandarin, displaying an alternate bearing behavior with heavy flower load in one year (‘On year’), followed by a relatively lighter flower load in the following year (‘Off year’), were sprayed with gibberellins during flower induction period of ‘On’ and ‘Off’ years. Buds, collected monthly until flower buds could be identified, included two populations, one from ‘Off year’ gibberellins-treated trees containing nearly 10% flower buds, and the second, from non-treated ‘On year’ trees containing nearly 90% flower buds. Transcription profiles of these two populations were compared using GeneChip® Citrus Genome Array (Affymetrix). Data analysis and expression analyses by RT-PCR indicated significant difference in transcript level of Citrus homologous of several meristem identity genes. The results of these analyses will be presented, and discussed in relation to the flowering control model of Arabidopsis.