EXPRESSION AND CIS-ACTING ELEMENTS OF THE AT-BETA-FRUCT1 GENE FROM ARABIDOPSIS-THALIANA ENCODING A CELL-WALL INVERTASE

The At beta fruct1 gene from Arabidopsis thaliana encodes a cell wall beta-fructosidase (invertase), one of three types of beta-fructosidase s purified from higher plants. Southern blots have shown that one copy of At beta fruct1 is present per haploid genome. Northern blots and R everse Transcriptase-Polymerase Chain Reaction analysis demonstrate th at the At beta fruct1 gene is expressed in roots, stems and leaves wit h the highest level of expression being found in roots. An 0.4 kb frag ment of the 5' region of the At beta fruct1 gene, located immediately upstream of the start of transcription, is sufficient to drive express ion of the reporter gene uida (GUS) in transgenic tobacco plants and p rotoplasts derived from a suspension line of A. thaliana. At beta fruc t1 promoter fragments have been shown to mediate uida gene expression from the heterologous 35S CaMV TATA box. In order to identify cis-acti ng regulatory elements, the At beta fruct1 promoter was dissected, and various elements were fused to the reporter gene. Transient expressio n in protoplasts revealed three cis-acting regions of 123 bp, 32 bp an d 42 bp. The first, located between -148 and -25, is A/T rich, the sec ond, located between -180 and -148, contains a repeated element (GTCTG A) and the third, which is situated between -222 and -180, contains a putative wound-responsive element (TTGTGGAAACAAC). The regions contain ing the repeated element and the putative wound-responsive element dow n regulate reporter gene expression, whilst the A/T rich region has a stimulatory effect.