Cloning and characterization of NtSnRK2.7 and NtSnRK2.8 genes involved in abiotic stress responses from Nicotiana tabacum

Sucrose non-fermenting1-related protein kinase 2 (SnRK2) plays a key role in abiotic stress signaling in plants. In this study, gene structures, phylogeny, conserved motifs and promoters of NtSnRK2.7 and NtSnRK2.8 in tobacco have been analyzed. Phylogenetic analysis showed that NtSnRK2.7 and NtSnRK2.8 belong to subclass I and subclass III of SnRK2, respectively. They exhibited similar genomic structures, consisting of 9 exons and 8 introns. Subcellular localization showed the presence of NtSnRK2s in the cell membrane, cytoplasm and nucleus. Quantitative real-time PCR was used to analyze the expression patterns of NtSnRK2s in tobacco. NtSnRK2s were constitutively expressed strongly in roots, weakly in stems, and marginally in leaves. Abiotic stress response analyses revealed that NtSnRK2.7 and NtSnRK2.8 were involved in response to various abiotic stresses with different patterns: there was evidence that NtSnRK2.7 participated in abscisic acid-independent signaling pathways, while the transcription of NtSnRK2.8 was induced by abscisic acid treatment; NtSnRK2.7 responded much faster to salt and cold stress. Furthermore, expression of NtSnRK2.8 increased intensely and reached its maximum at 1 h under drought stress indicating that it is sensitive to osmotic stress. Our results suggest that NtSnRK2.7 and NtSnRK2.8 are involved in multiple stress response pathways in distinct ways.