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Abstract
BackgroundPotassium (K) is essential to plant growth and development. Foxtail millet (Setaria italic L.) is an important fodder grain crop in arid and semi-arid regions of Asia and Africa because of its strong tolerance to drought and barren stresses. The molecular mechanisms of physiological and biochemical responses and regulations to various abiotic stresses such as low potassium conditions in foxtail millet are not fully understood, which hinders the research and exploitation of this valuable resource.ResultsIn this research, we demonstrated that the millet variety Longgu 25 was the most insensitive variety to low potassium stress among other five varieties. The transcriptome analysis of Longgu 25 variety revealed a total of 26,192 and 26,849 genes from the K+-deficient and normal transcriptomic libraries by RNA-seq, respectively. A total of 1982 differentially expressed genes (DEGs) were identified including 866 up-regulated genes and 1116 down-regulated genes. We conducted a comparative analysis of these DEGs under low-K+ stress conditions and discovered 248 common DEGs for potassium deprivation among foxtail millet, rice and Arabidopsis. Further Gene Ontology (GO) enrichment analysis identified a series of candidate genes that may involve in K+-deficient response and in intersection of molecular functions among foxtail millet, rice and Arabidopsis. The expression profiles of randomly selected 18 candidate genes were confirmed as true DEGs with RT-qPCR. Furthermore, one of the 18 DEGs, SiMYB3, is specifically expressed only in the millet under low-K+ stress conditions. Overexpression of SiMYB3 promoted the main root elongation and improved K+ deficiency tolerance in transgenic Arabidopsis plants. The fresh weight of the transgenic plants was higher, the primary root length was longer and the root surface-area was larger than those of control plants after K+ deficiency treatments.ConclusionsThis study provides a global view of transcriptomic resources relevant to the K+-deficient tolerance in foxtail millet, and shows that SiMYB3 is a valuable genetic resource for the improvement of K+ deficiency tolerance in foxtail millet.
Highlights
Potassium (K) is essential to plant growth and development
The 4-leaf stage seedlings had reduced shoot and root growth and leaf blade height for most varieties of six foxtail millet varieties after they were grown in potassium deficient media (LK) for 10 days
The results indicate that genes in the categories of metabolic process may play crucial roles in responses to low-K+ stress among foxtail millet, rice and Arabidopsis
Summary
Potassium (K) is essential to plant growth and development. The molecular mechanisms of physiological and biochemical responses and regulations to various abiotic stresses such as low potassium conditions in foxtail millet are not fully understood, which hinders the research and exploitation of this valuable resource. Potassium (K) is one of the essential macronutrients required for plant growth and development and involves in many important physiological processes in plant cells, including osmoregulation, turgor pressure control, electrical neutralization, and enzyme activation [1]. The K+ concentration is generally within the range of 1 to 200 ppm Most plants are subjected to low K+ stress at some points during their development. Transcriptional regulation is an important mechanism of plants in response to low-K+ stress [8,9,10].
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