Cellulase Gene Expression in Ethylene-Treated Geranium Flowers

Abstract

Abscission of floral organs after pollination is a common phenomenon in many plant species. The time between induction and completion of the abscission process varies widely among species. Generally completion of abscission of floral structures is faster than abscission of leaves and fruits (2.5–8 h vs 10–48 h) [2]. Anatomical studies in the abscission zone (AZ) reveal cell separation in the middle lamella and extensive swelling and disorganization of the semicrystalline bundles, microfibrils, in the primary wall of the abscission zone cells. It has become evident that hormones participate and have a regulatory role in abscission. The plant hormone ethylene increases cell expansion, which generates mechanical forces facilitating cell separation, and increases expression of genes associated with abscission. Cell wall hydrolases such as cellulases are commonly associated with abscission [3]. In geranium (Pelargonium xhortorum), exogenous application of ethylene induces petal abscission within 2 hours of treatment [1]. In the present study, the expression of three cellulases, PCX10, PCX59 and PCX102 was investigated in geranium tissues including petal abscission zone. The effect of ethylene on the mRNA levels of the three cellulases was also determined.