Abstract
Root systems are instrumental for water and nutrient uptake and the anchorage of plants in the soil. Root regulating GL2-interacting repressors (GIRs) contain a Short RING-like Zinc-Finger (SRNF) domain, but there has been no comprehensive characterization about this gene family in any plant species. Here, we renamed the GIR-like proteins as SRNF proteins due to their conserved domain and identified 140 SRNF genes from 16 plant species including 24 GhSRNF genes in Gossypium hirsutum. Phylogenetic analysis of the SRNFs revealed both similarities and divergences between five subfamilies. Notably, synteny analysis revealed that polyploidization and whole-genome duplication contribute to the expansion of the GhSRNF gene family. Various cis-acting regulatory elements were shown to be pertinent to light, phytohormone, defense responsive, and meristem regulation. Furthermore, GhSRNF2/15 were predominantly expressed in root, whereas the expression of GhSRNF18 is positively correlated with the primary root (PR) length in G. hirsutum, quantified by quantitative real-time PCR (qRT-PCR). Over-expression of GhSRNF18 in Arabidopsis and virus-induced gene silencing (VIGS) of GhSRNF18 in G. hirsutum has revealed the role of GhSRNF18 in PR growth. The over-expression of GhSRNF18 in Arabidopsis resulted in an increase of meristematic activities and auxin accumulations in PRs, which were consistent with the transcriptomic data. Our results suggested that GhSRNF18 positively regulates PR growth. This study increased our understanding of the SRNF gene family in plants and provided a novel rationale for the further investigation of cotton root morphogenesis regulated by the GhSRNFs.
Highlights
Roots are vital organs in terrestrial higher plants, for water and nutrient uptake and for the anchorage of plants in the soil, but to protect plants from diverse pathogens (Petricka et al, 2012; Rich-Griffin et al, 2020)
Primary roots growth is determined by the rate of cell division in the root apical meristem (RAM) and cell elongation in the elongation zone (EZ), which is tightly regulated by a series of transcription factors and multiple phytohormones (Petricka et al, 2012; Vanstraelen and Benkova, 2012; Motte et al, 2019)
44 GL2-interacting repressors (GIRs)-like proteins were identified in G. arboreum, G. raimondii, and G. hirsutum by sequence alignments using the GL2-interacting repressor 1 (GIR1) and GL2interacting repressor 2 (GIR2) protein sequences (Supplementary Table 2)
Summary
Roots are vital organs in terrestrial higher plants, for water and nutrient uptake and for the anchorage of plants in the soil, but to protect plants from diverse pathogens (Petricka et al, 2012; Rich-Griffin et al, 2020). Total root growth depends on two processes: cell elongation in the elongation zone and cell proliferation in proximal meristems (Camacho-Cristobal et al, 2015). PLT1 and PLT2 in Arabidopsis are redundantly required for distal cell division patterns and stem cell maintenance in root meristem in an auxin-dependent manner (Aida et al, 2004). Rapid cell expansion in the elongation zone (EZ) contributes to primary root growth and is largely regulated by plant hormones, including abscisic acid (ABA), brassinosteroids (BR), cytokinin, ethylene, gibberellic acid (GA), and auxin (IAA) (Petricka et al, 2012). Loss of function mutations in cellulose synthesis, such as rsw and procuste, result in cell expansion defects (Arioli et al, 1998; Fagard et al, 2000)
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