EXPRESSION OF TWO CHLOROPHYLL DEGRADATION GENES IN BROCCOLI UNDER POSTHARVEST HORMONAL TREATMENTS

BÜCHERT A; CIVELLO PM; MARTÍNEZ GA

Tucumán

Congreso; XLV Reunión Anual SAIB; 2009

SAIB

Harvesting of broccoli (Brassica oleracea) induces an early onset ofsenescence, characterized by a rapid degradation of chlorophylls.CHLOROPHYLLASE catalyzes phytol cleavage from chlorophylland has traditionally been considered to be the first step in thechlorophyll degradation pathway. In recent publications, it has beenstated that is PHEOPHYTINASE instead of CHLOROPHYLLASEthe responsible for phytol cleavage during senescence. In thecurrent work, we analyzed the expression by qPCR of knownbroccoli CHLOROPHYLLASEs (BoCLH) and a putativePHEOPHYTINASE from broccoli (BoPPH). Expression wasanalyzed using cytokine and ethylene treated broccoli and differentsections of the florets were compared. Relative expression resultsfrom qPCR experiments showed no direct correlation betweenBoCLH expression and normal or hormone-regulated senescence.In the case of BoPPH, an increase in expression was found with thecourse of senescence followed by a gradual decrease. In cytokinetreated samples, BoPPH expression was reduced and an increasewas found in ethylene treated samples. These results suggest thepossibility that phytol cleavage during chlorophyll degradation inpostharvest broccoli is performed by BoPPH and not BoCLH, aswas previously assumed, and thus reinforcing the recently arisentheory of PPH being the responsible for this important enzymaticstep.