Developmental stimuli and stress factors affect expression of ClGLP1, an emerging allergen-related gene in Citrus limon

Germins and germin-like proteins (GLPs) constitute an ubiquitous family of plant proteins that seem tobe involved in many developmental and stress related processes. A novel GLP cDNA was isolated fromCitrus limon and structural features and genomic organization were investigated by in silico and Southernblots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPsproteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group oflarge GLP family. ClGLP1 was differentially expressed in the various organs and was highest in maturefruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agriculturalpractice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced inyellow mature fruit from organic compared with conventional culture. A sudden and systemic increase inClGLP1 expression level was observed in leaves injured by wounding, together with an increase ofendogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transitionfrom green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulatedin relation to both developmental stimuli and culture practices; evidence is also provided that throughan oxidase activity this gene could play a role in fruit maturation as well as in stress responses.