Poster: Respiratory Pathways

Abs # 264: Thermoscopic identification of heat-generating cells that co-express both SfAOX and SfUCPb genes in the spadix of skunk cabbage, Symplocarpus foetidus

Presenter:	Ito, Kikukatsu , kikuito@iwate-u.ac.jp
Authors	Ito, Kikukatsu  (A)   Onda, Yoshihiko  (A)
Affiliations:	(A): Cryobiosystem Research Center, Iwate University

The spadix of skunk cabbage, Symplocarpus foetidus, which blooms in early spring, has been shown to maintain an internal temperature of around 20^oC even when the external air temperature drops below freezing. The mechanism of such homeothermic heat production in plants has been largely attributed to alternative oxidase (AOX) which is present in the inner membrane of mitochondria. Recently, however, mitochondrial uncoupling proteins (UCPs), which are implicated as a major heat generator in mammalian cells, have also been shown to exist in the thermogenic spadix of skunk cabbage. Although these observations suggest that AOX and UCPs, functionally distinct mitochondrial proteins, are involved in the thermoregulation in skunk cabbage, little is known about the functional contribution of these proteins. To better understand the role of AOX and UCP genes in the thermogenic cells of skunk cabbage, detailed thermoscopic analysis using an infrared thermal camera and examination of gene expressions of AOX and UCP were conducted. First, our analysis of the surface temperature of the longitudinal section of the thermogenic spadix successfully revealed that the florets in the spadix displayed increased temperature during the measurements. Second, in situ hybridization using SfUCPb, which is a major UCPs species in skunk cabbage, and SfAOX anti-sense RNA probes have shown that the expressions of both gene transcripts are co-localized in the thermogenic florets. Interestingly, probable thermogenic cells that co-express both SfAOX and SfUCPb transcripts were found to be surrounding the stamens in the florets. These observations strongly suggest a possible participation of both SfAOX and SfUCPb gene products in the homeothermic heat production in the spadix of skunk cabbage.