Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 2005
Publication Date: January 20, 2006
Citation: Matsumoto Brower, T.K. 2006. Genes uniquely expressed in vegetative and potassium chlorate induced floral buds of dimocarpus longan. Plant Science, 170:500-516. Interpretive Summary: Potassium chlorate is an effective method to produce off season longan or dragon eye fruit. To understand how potassium chlorate is able to induce flowering and subsequent fruit formation we isolated messenger RNA from buds that will become shoots on longan trees not treated with potassium chlorate and from buds that will become flowers on longan trees treated with potassium chlorate. The messenger RNA from both types of buds were used a template to create a complementary copy of the messenger RNA called cDNA. By mixing the cDNA from the buds that form shoots together with the buds the form flowers and removing the cDNA that are the present in both types of buds we are able to isolate the cDNA that are more abundant in either shoots or flowers. If genes are more highly expressed in flower buds, they may play a role in flowering or if genes are more highly expressed in shoots, they may promote vegetative growth or perhaps inhibit flowering. Using this procedure we have identified genes that were previously associated with flowering, potential gene families in which different members may play a role in flowering and novel genes that encode regulatory proteins not previously associated with flowering. Genes identified in this study will be further characterized to determine if they are important regulators of flowering in longan and other fruit trees.
Technical Abstract: Potassium chlorate (KClO3) induced flowering of Dimocarpus longan is a highly effective method for off-season fruit production in South East Asia. To begin to understand the molecular basis for longan flower induction, the suppression subtractive hybridization (SSH) technique was used to isolate genes that are differentially expressed in vegetative buds, or in KClO3 induced floral buds. Repetitive rounds of cDNA differential subtraction screening, followed by reverse northern, northern blot analysis and nucleotide sequence determination identified 65 unique genes differentially expressed in vegetative and floral buds. Many of the identified genes have been previously demonstrated to be associated with shoot and floral meristem in Arabidopsis, including PROTODERMAL FACTOR 1 (LVFS-205), SHEPHERD (LVFS-100) and PISTILLATA (LVFS-199) homologs. These gene sequences validate the results of SSH procedure and represent new nucleotide sequences in longan. Hybridization of clones to different size transcripts that encode fructose-bisphophate aldolase (LVFS-230), histone H3 (LVFS-44, LVFS-172), malonyl-CoA (LVFS-48) and SAM (sterile alpha motif) containing proteins (LVFS-290) suggest specific members of gene families or alternative splicing of RNA may be involved in longan flowering. Novel gene products not previously associated with flowering have been also identified including CCR4 (Carbon Catabolite Repressor)-associated factors (LVFS-323), SAM proteins (LVFS-290), and notchless-like proteins (LVFS-65). These cDNA sequences represent proteins with potential regulatory roles in longan flowering.