An Aquaglyceroporin Is Abundantly Expressed Early in the Development of the Suspensor and the Embryo Proper of Loblolly Pine (Pinus taeda L.)

In contrast to angiosperms, pines and other gymnosperms form well-developed suspensors in somatic embryogenic cultures. This creates a useful system to study suspensor biology. In a study of gene expression during the early stages of conifer embryogenesis, we identified a transcript, PtNlPl;l, that is abundant in immature Pinus taeda zygotic and somatic embryos, but is undetectable in later-stage embryos, megagametophytes and roots, stems and needles from 1 year-old seedlings. Analysis of PtNIPl;l transcript in embryo proper and suspensor tissues by RT-PCR suggests preferential expression in the suspensor. Based on comparisons of derived amino acid sequences, PtNIPl;l belongs to the NIP branch of the aquaporin (MIP) superfamily. Through heterologous expression in Xenopus laevis oocytes and the Saccharomyces cerevisiae fpsl" mutant, PtNIPl;! has been shown to be an active aquaglyceroporin.