Ovule-specific expression of the genes for mitochondrial and endoplasmic reticulum localized small heat-shock proteins in tomato flower

Tomato (Lycopersicon esculentum Mill.) mitochondrial small heat-shock protein (MT-sHSP) gene is known to respond quickly to heat stress in the leaves. To elucidate the role of sHSPs under heat stress in the reproductive organs and developing fruits, we examined the expression of the gene for MT-sHSP. In addition, the expression profiles of the genes for the cytosolic (class I and II) and endoplasmic reticulum (ER) localized small heat-shock proteins (class I-, class II- and ER-sHSP, respectively) were also examined. Although the examined genes were not or weakly expressed at a normal growth temperature, they all significantly responded to heat stress. In the flower, MT- and ER-sHSP were accumulated not in the pollen, but in the ovule. The expression profile suggests a role for sHSPs in protection against heat stress.