Effects of Various Elicitors on the Transcription of a β-1,3-endoglucanase Gene in Citrus Fruit

Very little is yet known regarding the molecular mech- anisms involved in pathogen defense responses in citrus fruit. Recently, a basic b-1,3-endoglucanase (EC 3.2.2.39) belonging to the pathogenesis-related (PR) group of proteins, has been puri®ed from Citrus sinensis (L) Osbeck cv. `Valenciaʹ orange callus. Speci®c anti- bodies raised against the puri®ed protein were used to screen `Valenciaʹ callus and ¯avedo cDNA expression libraries, and to isolate its corresponding cDNA, desig- nated gns1. The gns1 gene encodes a predicted poly- peptide of 336 amino acids with a molecular mass of 37.3 kDa and a basic pI of 9.19, and shares 55±65% identity with several other plant b-1,3-endoglucanase proteins. Hereby, we show that the expression of the gns1 gene is markedly induced by wounding and inoculation with Penicillium digitatum (Pers. Fr.) Sacc., and following treatments with various elicitors that induce fruit resistance against P. digitatum. These treatments include UV irradiation, application of jas- monic acid (JA), b-aminobutyric acid (BABA), Candida oleophila antagonist yeast cells and hot water rinsing and brushing. Overall, based on various RNA gel blot hybridizations, we assume that gns1 is most likely to be part of the molecular mechanisms involved in pathogen defense responses in citrus fruit.