Expression of the HEV2.1 gene promoter in transgenic Hevea brasiliensis

Hevein is involved in the coagulation of rubber particles and is known to be highly expressed in latex cells from Hevea brasiliensis. As all HEVEIN genes are highly conserved in their transcribed region, a promoter functional analysis was carried out in transgenic rubber tree in order to evaluate the expression of HEV2.1, one member of the HEVEIN multigenic family. Three out of the 14 established independent transgenic lines carrying the HEV2.1::GUS construct were selected and set to regenerate plantlets. In situ hybridization of transgenic and wild-type plant tissues was respectively carried out with gusA and HEVEIN antisense mRNA probes. This showed co-localized-expression of the HEV2.1 gene with the overall HEVEIN gene expression. Laticifer-specific expression was observed in roots and stems, but not in leaves where HEVEIN genes were expressed in all cell types. Since HEV2.1::GUS callus lines responded significantly to light stimulation, up-regulation of the expression of HEV2.1 genes by light was suggested in leaves.