Identification of heavy metal pollutant tolerance-associated genes in Avicennia marina (Forsk.) by suppression subtractive hybridization.

The halophytic Avicennia marina (Forsk.) is one of the pioneer mangroves along the south coast of China. It is an appropriate material for understanding molecular mechanisms of heavy metal tolerance in mangrove plants. A forward and a reverse cDNA library was constructed by PCR-based suppressive subtractive hybridization (SSH) to isolate these tolerance-associated genes from A. marina leaves. A total of 99 ESTs obtained from the forward and reverse libraries showed significant differential expressions. Twenty-nine genes selected by SSH were studied by real-time PCR in order to analyze their expression level. Most of these genes' expression increased in leaves under Cd stress, which suggests that these genes contribute to the heavy metal tolerance in A. marina. The diversity of these genes indicated that heavy metal stress resulted in a complex response in mangrove plants. This could prove a useful approach for further exploring the molecular mechanisms behind such heavy metal tolerance.
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