Abstract
BackgroundPhytohormone abscisic acid (ABA) is involved in the regulation of a wide range of biological processes. In Arabidopsis, it has been well-known that SnRK2s are the central components of the ABA signaling pathway that control the balance between plant growth and stress response, but the functions of ZmSnRK2 in maize are rarely reported. Therefore, the study of ZmSnRK2 is of great importance to understand the ABA signaling pathways in maize.ResultsIn this study, 14 ZmSnRK2 genes were identified in the latest version of maize genome database. Phylogenetic analysis revealed that ZmSnRK2s are divided into three subclasses based on their diversity of C-terminal domains. The exon-intron structures, phylogenetic, synteny and collinearity analysis indicated that SnRK2s, especially the subclass III of SnRK2, are evolutionally conserved in maize, rice and Arabidopsis. Subcellular localization showed that ZmSnRK2 proteins are localized in the nucleus and cytoplasm. The RNA-Seq datasets and qRT-PCR analysis showed that ZmSnRK2 genes exhibit spatial and temporal expression patterns during the growth and development of different maize tissues, and the transcript levels of some ZmSnRK2 genes in kernel are significantly induced by ABA and sucrose treatment. In addition, we found that ZmSnRK2.10, which belongs to subclass III, is highly expressed in kernel and activated by ABA. Overexpression of ZmSnRK2.10 partially rescued the ABA-insensitive phenotype of snrk2.2/2.3 double and snrk2.2/2.3/2.6 triple mutants and led to delaying plant flowering in Arabidopsis.ConclusionThe SnRK2 gene family exhibits a high evolutionary conservation and has expanded with whole-genome duplication events in plants. The ZmSnRK2s expanded in maize with whole-genome and segmental duplication, not tandem duplication. The expression pattern analysis of ZmSnRK2s in maize offers important information to study their functions. Study of the functions of ZmSnRK.10 in Arabidopsis suggests that the ABA-dependent members of SnRK2s are evolutionarily conserved in plants. Our study elucidated the structure and evolution of SnRK2 genes in plants and provided a basis for the functional study of ZmSnRK2s protein in maize.
Highlights
Phytohormone abscisic acid (ABA) is involved in the regulation of a wide range of biological processes
We found that ZmSnRK2.10 gene, which belongs to subclass III, was activated by ABA in maize
Comparative analysis showed that ZmSnRK2s were clustered into three subclasses, in which ZmSnRK2.12 with ZmSnRK2.8, ZmSnRK2.9 and ZmSnRK2.10 was classified as subclass III, while ZmSnRK2.13 and ZmSnRK2.14 with ZmSnRK2.4, ZmSnRK2.5, ZmSnRK2.6, ZmSnRK2.7 and ZmSnRK2.11 were clustered into subclass I
Summary
Phytohormone abscisic acid (ABA) is involved in the regulation of a wide range of biological processes. Phytohormone abscisic acid (ABA) is widely involved in plant growth and development, responses to biotic and abiotic stresses, as well as crop grain filling and seed maturation processes [1, 2]. Subclass III SnRK2s include three genes, SAPK8, SAPK9, and SAPK10 which are homologous to Arabidopsis SnRK2.2, SnRK2.3, and SnRK2.6 respectively These three SnRK2 proteins are activated by ABA [10, 20]. Compared with Wild type (WT), transgenic rice lines overexpressing SAPK8, SAPK9, or SAPK10 show delayed germination and seedling growth [21], suggesting that the subclass III SnRK2s in rice is involved in the regulation of seeds germination
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