A beta-galactosidase gene is expressed during mature fruit abscission of 'Valencia' orange (Citrus sinensis).
beta-galactosidases have been detected in a wide range of plants and are characterized by their ability to hydrolyse terminal non-reducing beta-D-galactosyl residues from beta-D-galactosides. These enzymes have been detected in a wide range of plant organs and tissues. In a search for differentially expressed genes during the abscission process in citrus, sequences encoding beta-galactosidase were identified. Three cDNA fragments of a beta-galactosidase gene were isolated from a cDNA subtraction library constructed from mature fruit abscission zones 48 h after the application of a mature fruit-specific abscission agent, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole). Based on sequence information derived from these fragments, a full-length cDNA of 2847 nucleotides (GenBank accession number AY029198) encoding beta-galactosidase was isolated from mature fruit abscission zones by 5'- and 3'-RACE approaches. The beta-galactosidase cDNA encoded a protein of 737 amino acid residues with a calculated molecular weight of 82 kDa. The deduced protein was highly homologous to plant beta-galactosidases expressed in fruit ripening. Southern blot analysis demonstrated that at least two closely related beta-galactosidase genes were present in 'Valencia' orange. Temporal expression patterns in mature fruit abscission zones indicated beta-galactosidase mRNA was detected 48 h after treatment of CMN-pyrazole and ethephon in mature fruit abscission zones. beta-galactosidase transcripts were detected in leaf abscission zones only after ethephon application. The citrus beta-galactosidase was expressed in stamens and petals of fully opened flowers and young fruitlets. The results suggest that this beta-galactosidase may play a role during abscission as well as early growth and development processes in flowers and fruitlets.
Wu
Zhencai
Z
University of Florida, IFAS, Horticultural Sciences Department, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, Florida 33850-2299, USA.
Burns
Jacqueline K
JK
D000595:Amino Acid Sequence; D001483:Base Sequence; D032084:Citrus sinensis / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D017931:DNA Primers; D005638:Fruit / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001616:beta-Galactosidase / Q000235:genetics*
D017931:DNA Primers; D012333:RNA, Messenger; D001616:beta-Galactosidase