Salicylic acid accumulation correlates with low anthocyanin production in Arabidopsis

Abstract

Anthocyanins, flavonoid pigments, are essential photoprotective agents and play a pivotal role in enhancing plant resilience to environmental stressors. It has been shown that anthocyanin production is inhibited when pattern-triggered immunity (PTI) is activated in Arabidopsis thaliana. An important component of PTI is the phytohormone salicylic acid (SA). Interestingly, exogenous treatment with SA has been shown to induce anthocyanin content in grape, apple, maize roots, rose callus, or Arabidopsis seedlings. In this study, we used several A. thaliana mutants with modulated SA content to decipher the role of endogenous SA in anthocyanin production in A. thaliana. We treated WT and mutants with anthocyanin-inducible conditions and measured anthocyanin content using spectroscopy. We showed that high endogenous SA accumulation correlates with low anthocyanin production. This was confirmed by the treatment of the A. thaliana seedlings with exogenous SA. Additionally, using microscopy in the 5gt mutant, which exhibits enhanced production of anthocyanin vesicular inclusions (AVIs) due to the inhibition of ligandin-dependent vacuolar import, we showed that high endogenous SA also correlates with lower AVI abundance. Comparative analysis of Arabidopsis WT and mutants used in this study indicates a possible inhibitory effect of SA accumulation on anthocyanin content under anthocyanin-inducible conditions (AICs). We suggest that under AICs, SA downstream signaling independent of NPR1 is responsible for lower anthocyanin accumulation. HighlightsO_LIHigh endogenous SA correlates with low anthocyanin content under AIC in Arabidopsis C_LIO_LISA signaling, not biosynthesis, is responsible for the inhibition of anthocyanins C_LIO_LIHigh SA concentration decreases the abundance of AVI bodies C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=146 HEIGHT=200 SRC="FIGDIR/small/658514v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@183500corg.highwire.dtl.DTLVardef@1fc5e3forg.highwire.dtl.DTLVardef@18fb48forg.highwire.dtl.DTLVardef@1975181_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract. Anthocyanin-inducible conditions (AICs), such as changes in day length, high sucrose in the medium, or treatment with kinetin, trigger the biosynthesis of anthocyanins. Previously, it was shown that activated pattern-triggered immunity (PTI), caused by the recognition of microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs), inhibits anthocyanin production. A typical PTI response is an increased production of salicylic acid (SA). In this study, we show that a high concentration of SA and its downstream signaling, rather than SA biosynthesis itself, reduces anthocyanin accumulation.