Exogenous GA3 Application Enhances Xylem Development and Induces the Expression of Secondary Wall Biosynthesis Related Genes in Betula platyphylla

Abstract

Gibberellin (GA) is a key signal molecule inducing differentiation of tracheary elements, fibers, and xylogenesis. However the molecular mechanisms underlying the effect of GA on xylem elongation and secondary wall development in tree species remain to be determined. In this study, Betula platyphylla (birch) seeds were treated with 300 ppm GA3 and/or 300 ppm paclobutrazol (PAC), seed germination was recorded, and transverse sections of hypocotyls were stained with toluidine blue; the two-month-old seedlings were treated with 50 μM GA3 and/or 50 μM PAC, transverse sections of seedling stems were stained using phloroglucinol–HCl, and secondary wall biosynthesis related genes expression was analyzed by real-time quantitative PCR. Results indicated that germination percentage, energy and time of seeds, hypocotyl height and seedling fresh weight were enhanced by GA3, and reduced by PAC; the xylem development was wider in GA3-treated plants than in the control; the expression of NAC and MYB transcription factors, CESA, PAL, and GA oxidase was up-regulated during GA3 treatment, suggesting their role in GA3-induced xylem development in the birch. Our results suggest that GA3 induces the expression of secondary wall biosynthesis related genes to trigger xylogenesis in the birch plants.

Root-to-Shoot Hormonal Communication in Contrasting Rootstocks Suggests an Important Role for the Ethylene Precursor Aminocyclopropane-1-carboxylic Acid in Mediating Plant Growth under Low-Potassium Nutrition in Tomato

“…GAs were also detected in the root xylem sap and numerous studies suggest that these hormones interact with mineral nutrition (Rubio et al, 2009), as for K (Wakhloo, 1970; Chen et al, 2001), P, and Fe (Guo et al, 2015). By comparing the two contrasting graft combinations responding negatively ( HcLk ) or positively ( LcHk ) to low-K, GA 1 , GA 3 , and GA 4 levels decreased in the former while they were not affected in the later, contrarily to that observed for ACC, which suggest that GAs and ACC could be interacting in the rootstock-mediated response to low-K, as supported by the negative correlations found between those hormones in the root xylem sap (data not shown).…”

“…By comparing the two contrasting graft combinations responding negatively ( HcLk ) or positively ( LcHk ) to low-K, GA 1 , GA 3 , and GA 4 levels decreased in the former while they were not affected in the later, contrarily to that observed for ACC, which suggest that GAs and ACC could be interacting in the rootstock-mediated response to low-K, as supported by the negative correlations found between those hormones in the root xylem sap (data not shown). Applying GA 3 enhances K uptake in rice (Chen et al (2001), which is required for stem elongation, but also enhances micronutrient uptake, such as Fe and Mn (Guo et al, 2015), two micronutrients that are particularly high in the tolerant LcHk plants (Table 1). …”

Effects of Gibberellin and Gibberellin Biosynthesis Inhibitor (Paclobutrazol) Applications on Radish (Raphanus sativus) Taproot Expansion and the Presence of Authentic Hormones

“…The variation in xylem, cortex and vessel cells in radish root were associated with changes, which lead to increase the thickness of the radish taproot. In general, root thickening occurred by a combination of cell division and cell enlargement (Bidadi et al, 2010;Guo, et al, 2015;Wang et al, 2015;Mabvongwe et al, 2016).…”

Transcriptomic Analysis Provides Insights into Grafting Union Development in Pecan (<em>Carya illinoinensis</em>)

“…Accordingly, 248 one GA synthesis gene, GA20ox, were highly up-regulated after grafting and achieved its peak 249 expression at 30d, while three GA deactivating genes, GA2ox, were all significantly down-regulated 250 at 30d (Fig 5). GA signaling could promote the expression of genes involved in cell expansion as well 251 as secondary wall biosynthesis during xylem differentiation [31,32]. For the genes involved in GA 252 signaling, we found that one unigene encoding GID1, a gibberellin receptor, was up-regulated 253 strikingly at 30d, which might take part in vasculature formation.…”