Abstract
Wild watermelon from the Kalahari desert has an ability to survive drought/high light stress. To identify genes induced in the stressed leaves, we used mRNA differential display analyses and isolated a cDNA that encodes a homologue of mammal cytochrome b561, named CLCyb561-A. A cDNA encoding another homologue, CLCyb561-B was isolated by degenerate PCR. RNA gel blot analyses revealed that the expression of CLCyb561-A was induced, while that of CLCyb561-B was repressed gradually under drought/high light stress. However, protein blot analyses showed that the accumulation level of the CLCyb561-B protein was unchanged during the stress. Transient expression assays using CLCyb561-GFP fusions demonstrated that both CLCyb561-A and B proteins were localized in the plasma membrane. Mammal cytochrome b561 functions for transferring electrons across the adrenal chromaffin granule membrane in the synthesis of noradrenarine in the organelle. We propose a model that CLCyb561s participate in the dissipation of excess reducing energy.
