Expression of the Arabidopsis thaliana invertase gene family

Cell-wall and vacuolar invertases (beta-D-fructofuranosidase, EC 3.2.1.26) from Arabidopsis thaliana (L.) Heynh. are encoded by at least four genes, n amely At beta fruct1, At beta fruct2, At beta fruct3 and At beta fruct4. Di fferent A. thaliana organs from four developmental stages and under differe nt environmental conditions were analyzed for invertase gene expression. Ou r results clearly show that both the cell-wall and vacuolar invertase genes are expressed in a development and organ-specific manner. No transcripts o f the cell-wall invertase gene Ar beta fruct1 were found in the cotyledons; however, relatively high levels were detected in the leaves of mature plan ts. The expression of the second cell-wall gene At beta fruct2 was found to be flower-specific, conversely no expression of At beta fruct1 was detecte d in flowers. The vacuolar gene At beta fruct3 shows a distinctly different regulation of expression from At beta fruct1. Northern and reverse transcr iptase-polymerase chain reaction analyses revealed the presence of transcri pts in the cotyledons and only low levels in leaves, roots and flower buds. The second vacuolar invertase gene, At beta fruct4, was found to be expres sed in leaves of very young plants, but no transcripts were detected in the leaves of mature flowering plants. In order to investigate the respective roles of invertases and sucrose synthase, a comparative analysis of the exp ression of these genes was carried out. The present study shows that cell-w all and vacuolar invertase genes are differentially regulated by environmen tal factors.