Abstract
Rapid and extensive rhizome development is a desirable trait for perennial grass growth and adaptation to environmental stresses. The objective of this study was to determine proteomic changes and associated metabolic pathways of gibberellin (GA) -regulation of rhizome elongation in two perennial grass species differing in rhizome development. Plants of a short-rhizome bunch-type tall fescue (TF; Festuca arundinacea; ‘BR’) and an extensive rhizomatous Kentucky bluegrass (KB; Poa pratensis; ‘Baron’) were treated with 10 μM GA3 in hydroponic culture in growth chambers. The average rhizome length in KB was significantly longer than that in TF regardless of GA3 treatment, and increased significantly with GA3 treatment, to a greater extent than that in TF. Comparative proteomic analysis using two-dimensional electrophoresis and mass spectrometry was performed to further investigate proteins and associated metabolic pathways imparting increased rhizome elongation by GA. A total of 37 and 38 differentially expressed proteins in response to GA3 treatment were identified in TF and KB plants, respectively, which were mainly involved in photosynthesis, energy and amino acid metabolism, protein synthesis, defense and cell development processes. Accelerated rhizome elongation in KB by GA could be mainly associated with the increased abundance of proteins involved in energy metabolism (glyceraldehyde-3-phosphate dehydrogenase, fructose-bisphosphate aldolase, and ATP synthase), amino acid metabolism (S-adenosylmethionine and adenosylhomocysteinase), protein synthesis (HSP90, elongation factor Tu and eukaryotic translation initiation factor 5A), cell-wall development (cell dividion cycle protein, alpha tubulin-2A and actin), and signal transduction (calreticulin). These proteins could be used as candidate proteins for further analysis of molecular mechanisms controlling rhizome growth.
Highlights
Rhizomes are underground stems with meristematic tissues in rhizome nodes capable of generating shoots and roots, which serve as an important storage organ for carbohydrates, nutrients and water in perennial grass species (Jernstedt and Bouton, 1985; Li and Beuselinck, 1996)
Based on the functional analysis, the GA3-responsive proteins in tall fescue (TF) were mainly categorized into photosynthesis (10.81%), energy metabolism (24.32%), amino acid metabolism (21.62%), protein synthesis (13.51%), defense (5.41%), cell development (5.41%), transport (5.41%), RNA transcription (2.7%), and unknown proteins (10.81%; Figure 5A); the GA3-responsive proteins in Kentucky bluegrass (KB) were mainly categorized into photosynthesis (42.11%), energy metabolism (10.53%), amino acid metabolism (7.89%), protein synthesis (15.79%), defense (7.89%), cell development (7.89%), signal transduction (2.63%), and unknown proteins (5.26%; Figure 5B)
Our previous study indicated that the transcript levels of ent-kaurene oxidase, GA 20-oxidase1 and DELLA involved in GA metabolism and signaling pathways were increased in rhizomes with GA3 treatment compared with the control in TF, expansin and endotransglucosylase/hydrolases family genes responsible for GA treatment were increased with exogenously applied GA3 in TF rhizomes (Ma et al, submitted)
Summary
Rhizomes are underground stems with meristematic tissues in rhizome nodes capable of generating shoots and roots, which serve as an important storage organ for carbohydrates, nutrients and water in perennial grass species (Jernstedt and Bouton, 1985; Li and Beuselinck, 1996). Some growth-related regulators are found to be enriched in rhizomes, such as the elongation factor, tubulin alpha-3 chain, growth regulating factor in wild rice (He et al, 2014; Zhang et al, 2014), nuclear RNA-binding proteins, mitogen-activated protein kinase, proteasome regulatory particle triple-A ATPase subunit and elongation factor in wild sorghum (Jang et al, 2006), and cell division control 20 and histone H4 in sacred lotus (Kim et al, 2013) These studies suggest that aforementioned proteins and genes could play important roles in rhizome development. The underlying mechanisms or metabolic factors regulating rhizome growth in perennial grass species are largely unknown
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