Two homeologous MATE transporter genes, NtMATE21 and NtMATE22, are involved in the modulation of plant growth and flavonol transport in Nicotiana tabacum

Abstract

Multidrug and toxic compound extrusion (MATE) family has been implicated in the transport of a diverse range of molecules, including specialized metabolites. In Nicotiana tabacum, only a limited number of MATE transporters have been functionally characterized, and no MATE transporter has been studied in the context of flavonoid transport in this plant species so far. Here in the present study, we characterize two homeologous MATE genes, NtMATE21 and NtMATE22, and demonstrate their role in flavonol transport and in plant growth and development. The expression of these two genes was reported to be up-regulated in trichomes as compared to the trichome-free leaf. The transcript levels of NtMATE21 and NtMATE22 were found to be higher in flavonol over-producing tobacco transgenic lines as compared to wild type (WT) tobacco. The two transporters were demonstrated to be localized to the plasma membrane. Genetic manipulation of NtMATE21 and NtMATE22 led to altered growth phenotypes and modulated flavonol contents in N. tabacum. The GUS and GFP fusion transgenic lines of promoter regions suggested that NtMATE21 and NtMATE22 exclusively express in the trichome heads in the leaf tissue and petals. Moreover, in transient transactivation assay, NtMYB12, a flavonol-specific MYB transcription factor, was found to transactivate the expression of NtMATE21 and NtMATE22 genes. Together, our results strongly suggest the involvement of NtMATE21 and NtMATE22 in flavonol transport as well as in the regulation of plant growth and development.