Differential gene expression of the α-chain of mitochondrial H+-transporting ATP synthase between dormant and non-dormant seeds of paddy Echinochloa weeds

Gene expression was compared under favorable germination conditions between dormant and non-dormant seeds of rice paddy Echinochloa weeds and a domesticated Echinochloa species lacking dormancy. Two dormancy-specific cDNAs, Ecd1 and Ecd2 , were identified by differential display. Northern blot analysis revealed that these genes were more strongly expressed in dormant seeds than in non-dormant seeds. A database search for the Ecd1 sequence revealed no significant homology with any known proteins, but the Ecd2 sequence was highly homologous with the α-chain of mitochondrial H⁺-transporting adenosine triphosphate (ATP) synthase in rice ( Oryza sativa L.). These findings indicate that the gene encoding the enzyme associated with conventional aerobic respiration is more abundantly transcribed in dormant seeds. The results reported in the present study suggest that dormant seeds of paddy Echinochloa weeds, which appear during the period when paddy soil becomes aerobic by drainage, may maintain viability primarily by efficient conventional aerobic respiration, including ATP synthesis catalyzed by the mitochondrial H⁺-transporting ATP synthase.