Tissue-Specific Expression Analysis and Functional Validation of <i>SiSCR</i> Genes in Foxtail Millet (<i>Setaria italica</i>) Under Hormone and Drought Stresses, and Heterologous Expression in <i>Arabidopsis</i>
The SCARECROW (SCR) transcription factor governs cell-type patterning in plant roots and Kranz anatomy of leaves, serving as a master regulator of root and shoot morphogenesis. Foxtail millet (<i>Setaria italica</i>), characterized by a compact genome, self-pollination, and a short growt...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Plants |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2223-7747/14/14/2151 |
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| Summary: | The SCARECROW (SCR) transcription factor governs cell-type patterning in plant roots and Kranz anatomy of leaves, serving as a master regulator of root and shoot morphogenesis. Foxtail millet (<i>Setaria italica</i>), characterized by a compact genome, self-pollination, and a short growth cycle, has emerged as a C<sub>4</sub> model plant. Here, we revealed two <i>SCR</i> paralogs in foxtail millet—<i>SiSCR1</i> and <i>SiSCR2</i>—which exhibit high sequence conservation with <i>ZmSCR1/1h</i> (<i>Zea mays</i>), <i>OsSCR1/2</i> (<i>Oryza sativa</i>), and <i>AtSCR</i> (<i>Arabidopsis thaliana</i>), particularly within the C-terminal GRAS domain. Both <i>SiSCR</i> genes exhibited nearly identical secondary structures and physicochemical profiles, with promoter analyses revealing five conserved <i>cis</i>-regulatory elements. Robust phylogenetic reconstruction resolved <i>SCR</i> orthologs into monocot- and dicot-specific clades, with <i>SiSCR</i> genes forming a sister branch to <i>SvSCR</i> from its progenitor species <i>Setaria viridis</i>. Spatiotemporal expression profiling demonstrated ubiquitous <i>SiSCR</i> gene transcription across developmental stages, with notable enrichment in germinated seeds, plants at the one-tip-two-leaf stage, leaf 1 (two days after heading), and roots during the seedling stage. Co-expression network analysis revealed that there is a correlation between <i>SiSCR</i> genes and other functional genes. Abscisic acid (ABA) treatment led to a significant downregulation of the expression level of <i>SiSCR</i> genes in Yugu1 roots, and the expression of the <i>SiSCR</i> genes in the roots of An04 is more sensitive to PEG6000 treatment. Drought treatment significantly upregulated <i>SiSCR2</i> expression in leaves, demonstrating its pivotal role in plant adaptation to abiotic stress. Analysis of heterologous expression under the control of the 35S promoter revealed that <i>SiSCR</i> genes were expressed in root cortical/endodermal initial cells, endodermal cells, cortical cells, and leaf stomatal complexes. Strikingly, ectopic expression of <i>SiSCR</i> genes in <i>Arabidopsis</i> led to hypersensitivity to ABA, and ABA treatment resulted in a significant reduction in the length of the meristematic zone. These data delineate the functional divergence and evolutionary conservation of <i>SiSCR</i> genes, providing critical insights into their roles in root/shoot development and abiotic stress signaling in foxtail millet. |
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| ISSN: | 2223-7747 |