The Nodulin 26-like intrinsic membrane protein OsNIP3;2 is involved in arsenite uptake by lateral roots in rice.

Previous studies have shown that the Nodulin 26-like intrinsic membrane protein (NIP) Lsi1 (OsNIP2;1) is involved in arsenite [As(III)] uptake in rice (Oryza sativa). However, the role of other rice NIPs in As(III) accumulation in planta remains unknown. In the present study, we investigated the role OsNIP3;2 in As(III) uptake in rice. When expressed in Xenopus laevis oocytes, OsNIP3;2 showed a high transport activity for As(III). Quantitative real-time RT-PCR showed that the expression of OsNIP3;2 was suppressed by 5 µM As(III), but enhanced by 20 and 100 µM As(III). Transgenic rice plants expressing OsNIP3;2pro-GUS showed that the gene was predominantly expressed in the lateral roots and the stele region of the primary roots. Transient expression of OsNIP3;2:GFP fusion protein in rice protoplasts showed that the protein was localized in the plasma membrane. Knockout of OsNIP3;2 significantly decreased As concentration in the roots, but had little effect on shoot As concentration. Synchrotron microfocus X-ray fluorescence showed decreased As accumulation in the stele of the lateral roots in the mutants compared with wild-type. Our results indicate that OsNIP3;2 is involved in As(III) uptake by lateral roots, but its contribution to As accumulation in the shoots is limited.

Multiple Dlk1 splice variants are expressed during early mouse embryogenesis.

Delta-like homologue 1 (Dlk1), an atypical Notch ligand, is known to have roles in growth and development, stem cell maintenance, and cancer. Evidence suggests that Dlk1 expression patterns are more complex than previously appreciated, with multiple isoforms expressed in various tissues in both the embryo and adult. However, the early embryonic expression of Dlk1 has not been well examined. Given that tissue specific Dlk1 knockouts have to date failed to recapitulate phenotypes associated with the conventional Dlk1 loss of function model, a better understanding of early Dlk1 expression is important. To address this question, we have examined Dlk1 expression during the early stages of mouse embryogenesis. Dlk1 expression was first detected at Theiler Stage 14 (TS14), and its expression pattern persisted in specific tissues through TS20. Further, we found that all known Dlk1 splice isoforms were expressed in early embryogenesis, with Dlk1-A and Dlk1-C/C2 isoforms being expressed at the highest levels. The broad co-expression of multiple Dlk1 isoforms corroborates recent work suggesting that Dlk1-mediated signaling may act through multiple DLK1 isoforms to balance differentiation.