Expression analysis of genes encoding cell wall modifying enzymes during ripening of fig fruit (Ficus carica L. cv Masui Dauphine)

The fig fruit undergoes simultaneous ripening and increase in fruit size during its final stage of maturation. In an effort to understand the molecular basis of softening in figs, we isolated cDNAs responsible for cell wall expansion and disassembly, basically two cDNAs encoding two divergent Endo-1,4-β-glucanases (FC-Ce-l1 and FC-Cel-2, respectively) and three cDNAs encoding xyloglucan endotransglycosylase (FC-XET1, FC-XET2, FC-XET3 ) from ripe figs. The southern blot analyses indicate that the isolated XETs and EGases exist as single copy genes in the fig fruit genome. Propylene stimulated the accumulation of FC-Cel-1 mRNA while 1-Methylcyclopropane (MCP) inhibited its accumulation indicating that this gene is up-regulated by ethylene. FC-XET1 mRNA accumulation was detected only in the MCP treated fruit indicating that this gene is down-regulated by ethylene. FC-Cel-1 and FC-XET2 mRNAs showed a more or less constitutive expression in both treatments indicating that these genes are ethylene independent and are developmentally regulated. Significant accumulation of FC-XET3 transcript was detected on day 3 in all fruit irrespective of treatment, suggesting that this gene is ethylene independent and is stage specific. These results indicate that fig fruit XETs and EGases comprise gene families with divergent members showing differential regulation during fig fruit ripening. A combination of ethylene and developmental factors influence the expression of these genes suggesting that multiple activities are required for the cooperative modification of the hemicellulose network during softening of fig fruit.