Abstract:In para rubber tree (Hevea brasiliensis), HbSUT3 plays the role of key sucrose transporter (SUT) in sucrose loading into laticifers and rubber productivity, whereas HbSUT5 is putatively involved in the regulation of sucrose loading into laticifers. To further investigate the functions of the two SUT genes, digoxigenin-labeled cRNA probes were prepared, and used by in situ hybridization to detect the distribution patterns of HbSUT3 and HbSUT5 mRNAs in tissues of rubber young stems and midribs. The results showed that the two SUT genes were mainly expressed in phloem and cortex of barks in young stems, whereas they were expressed in all tissues of midribs except for xylem. The expressions of HbSUT3 were similar between young stems and midribs, while the expression of HbSUT5 in young stems was much higher than that in midribs. It was suggested that HbSUT3 and HbSUT5 could involve in activities, such as phloem loading, sucrose transportation and supply to sink cells, and they also had functional differentiation.