Identification of NtNIP2;1: an Lsi1 silicon transporter in Nicotiana tabacum

Abstract

Foliar silicon (Si) concentrations vary significantly among plants, resulting in the classification of different species as either high or low-Si accumulators. While the uptake pathways have been identified in some high accumulators, those that operate in low accumulators have largely been overlooked. Using a bioinformatics approach, a putative NIP2-like Si transporter gene was discovered within the genome of the low-Si accumulator, Nicotiana tabacum. The predicted protein, termed NtNIP2;1, possesses all the molecular signatures expected of an NIP2 Si transporter. Furthermore, when NtNIP2;1 was expressed in Xenopus oocytes, Si transport across the plasma membrane was observed. Nicotiana tabacum NIP2;1 RNA levels in the roots of seedlings were down-regulated in response to Si, similar to the Si transporter, OsLsi1, in rice. Taken together, these data suggest that a functional NIP2 Si uptake mechanism is also present in plants that acquire low foliar Si levels.