Sweet potato cDNAs that encode IbJ8, the smallest known J-domain protein, were isolated and characterized. This genome has at least two copies of IbJ8, which is expressed preferentially in the leaves, flowers, petioles, and stems. Spatial and temporal patterns were studied at different developmental stages, and expression was greater in younger leaves than in older ones. Moreover, expression in roots that arose from single-leaf cuttings was lower at 15, 20, and 30 d than at 40 d, and then the signal was undetectable at 60 d after planting. These results suggest that IbJ8 expression may be related to the organ age or developmental stage.