Thermogenesis in skunk cabbage (Symplocarpus renifolius): New insights from the ultrastructure and gene expression profiles

Floral thermogenesis has been found in several plant species. The spadix of one thermoregulatory plant, the Eastern Asian skunk cabbage (Symplocarpus renifolius), can maintain its temperature at approximately 22-26°C for several days, even when the ambient temperature falls below freezing. There are two major stages in skunk cabbage inflorescence development: the thermogenic female stage and the non-thermogenic male stage; in the former the spadix can produce massive amounts of heat, whereas in the latter, thermogenesis is undetectable. Based on previous studies, there is a positive correlation between heat production and the abundance of mitochondria in plant tissues and cells, and genes involved in cellular respiration and mitochondrial function are significantly enhanced at the female stage. Taken together, these findings suggest that the increased respiration or mitochondrial abundance observed in thermogenic tissues may be attributable to the high expression of specific genes. This review summarizes new insights into the changes in intracellular structures and gene expression profiles of skunk cabbage spadices during the female-male transition and proposes possible processes that are essential for each stage during floral development.