Light, the circadian clock, and sugar perception in the control of lignin biosynthesis

Abstract

Experiments were undertaken to investigate some of the mechanisms that may function to regulate lignin biosynthesis (lignification) in Arabidopsis thaliana. Northern blot analyses revealed that several genes encoding enzymes involved in the synthesis of lignin monomers displayed significant changes in transcript abundance over a diurnal cycle. Northern blot analysis also suggested that some of the changes in diurnal transcript abundance were likely to be attributable to circadian regulation, whereas others were likely to be attributable to light perception. Comparison of circadian changes in transcript abundance of lignin biosynthetic genes between wild-type plants and the sex1 mutant, which is impaired in starch turnover, suggested that carbon availability related to starch turnover might determine the capacity to synthesize lignins. This hypothesis was supported by the observation that the sex1 mutant accumulated fewer lignins than wild-type plants. Consistent with the relationship between carbon availability and lignin accumulation, analysis of dark-grown wild-type A. thaliana seedlings uncovered a role for sugars in the regulation of lignin biosynthesis. Analysis of lignin accumulation, as determined by qualitative changes in phloroglucinol staining, suggested that metabolizable sugars positively influence the abundance of lignins. Transcriptome analysis supports the hypothesis that sugars are not merely a source of carbon skeletons for lignification, but they also function as a signal to enhance the capacity to synthesize lignins.

A coumaroyl-ester-3-hydroxylase Insertion Mutant Reveals the Existence of Nonredundant meta-Hydroxylation Pathways and Essential Roles for Phenolic Precursors in Cell Expansion and Plant Growth

“…7A). This variation in gene expression is in agreement with studies by Rogers et al (2005), and a comparable cycling of all transcripts analyzed was also observed in cyp98A3 insertion mutants, with the exception of a total inactivation of CYP98A3 (Fig. 7A).…”

“…Given that genes encoding phenylpropanoid enzymes display diurnal changes in their expression (Rogers et al, 2005), we examined expression levels throughout the 12-h light cycle in plants grown under a 12-h-light/12-h-dark regime. In wildtype plants, the transcript levels of all phenylpropanoid genes were highest 4 h into the light period.…”

Light Regulation and Daytime Dependency of Inducible Plant Defenses in Arabidopsis: Phytochrome Signaling Controls Systemic Acquired Resistance Rather Than Local Defense

“…On the basis that some genes implicated in plant defense follow a circadian expression pattern, a link between defense and circadian signaling has been established previously (Sauerbrunn and Schlaich, 2004). Examples for such genes are Arabidopsis PCC1 (pathogen and circadian controlled 1) and PAL1 (Sauerbrunn and Schlaich, 2004;Rogers et al, 2005). The plant circadian clock maintains a relatively constant period, even in the absence of environmental cues such as light (Hotta et al, 2007).…”

“…Light might thus positively influence SA levels through photosynthesis and increased production of biosynthetic carbon precursors. Metabolizable sugars have been shown to positively influence secondary metabolism and defense gene expression in Arabidopsis, because they promote lignification in dark grown roots and induce PR transcript levels in seedlings (Thibaud et al, 2004;Rogers et al, 2005). As SA biosynthesis via isochorismate synthase occurs in plastids (Strawn et al, 2007), photosynthetic activity might be required to supply reducing equivalents and energy for SA accumulation.…”

Cultura de células em suspensão como ferramenta para estudos em parede celular secundária em gramí­neas C4

“…As culturas foram filtradas e 300 mg de células foram inoculadas em 30 mL de meios de indução distintos, diferindo na composição e concentração de hormônios, como evidenciado na Tabela 1. Os meios foram suplementados com sacarose, visto que este composto é não somente uma fonte de carbono, mas também um sinalizador no processo de lignificação (Rogers et al, 2005;Ogita et al, 2012).…”