Poster: Integrated Plant Biology

Abs # 84: Molecular cloning and expression of a cDNA encoding for b-galactosidase during mature fruit abscission in Valencia orange

Presenter:	Wu, Zhencai , wu@lal.ufl.edu
Authors	Wu, Zhencai  (A)   Burns, Jacqueline K. (A)
Affiliations:	(A): University of Florida

b-galactosidases are characterized by their ability to hydrolyze terminal non-reducing b-D-galactosyl residues from b-D-galactosides. These enzymes have been detected in a wide range of plant organs and tissues, and are associated with a number of plant processes involving cell wall modifications. We were interested in examining the involvement of b-galactosidase in abscission. Four cDNA fragments of a b-galactosidase gene were identified from a cDNA subtraction library constructed from mature Valencia fruit abscission zones 48 hours after application of a mature fruit-specific abscission agent 5-chloro-3-methyl-4-nitro-pyrazole (CMN-pyrazole). Based on sequence information derived from these fragments, a full-length cDNA of 2847 nucleotides in length (GenBank accession No. AY029198) encoding b-galactosidase was obtained. It encoded a predicted protein of 737 amino acid residues with a calculated molecular weight of 82.0 kDa and isoelectric point of 8.6. The deduced protein showed high levels of homology to plant b-galactosidases expressed in fruit ripening. Southern blot analysis demonstrated that at least two closely related b-galactosidase genes are present in Valencia orange. Temporal expression patterns in mature fruit abscission zones were examined by northern blot hybridization. The expression of b-galactosidase mRNA was detected 48 hours after induction of abscission with CMN-pyrazole. To our knowledge, this is the first report describing the expression of b-galactosidase during abscission. The results suggest that b-galactosidase may play a role in the abscission process of mature citrus fruit.