Flavonols modulate lateral root emergence by scavenging reactive oxygen species inArabidopsis thaliana

Abstract

Flavonoids are plant-specific antioxidant compounds that modulate plant development, which include flavonols and anthocyanins subclasses. In Arabidopsis thaliana, mutants in genes encoding each step in the flavonoid biosynthetic pathway have been isolated. We used these mutants to examine the role of flavonols in initiation and emergence of lateral roots and asked whether this regulation occurs through scavenging ROS. The tt4 mutants have a defect in the first committed step of flavonoid biosynthesis and have increased lateral root emergence. This phenotype was reversed by both genetic and chemical complementation. Using these flavonoid biosynthetic mutants, we eliminated roles for anthocyanins and the flavonols, quercetin and isorhamnetin, in controlling lateral root development. The tt7-2 mutant has a defect in a branchpoint enzyme blocking quercetin biosynthesis that led to elevated levels of kaempferol and reduced lateral roots. Kaempferol accumulated within lateral root primordia and was significantly increased in tt7-2. Thee data are consistent with kaempferol acting as a negative regulator of lateral root emergence. We examined ROS accumulation above and within the primordia using a general ROS sensor and identified increased signal above the primordia of the tt4 and tt7-2 mutants compared to wild type. Using a superoxide specific sensor, we detected a decrease in signal within the primordia of tt7-2, but not the tt4 mutant, compared to wild type. Together, these results support a model in which increased level of kaempferol in tt7-2 leads to a reduction in superoxide concentration in the lateral root primordia thereby reducing ROS-stimulated lateral root emergence.

Phosphorylation dynamics in a flg22-induced, heterotrimeric G-protein dependent signaling network in Arabidopsis thaliana reveals a candidate PP2A phosphatase involved in AtRGS1 trafficking

“…The foundation experiments designed to capture the relevant window of time and physiological concentration of flg22 for our subsequent phosphosite mapping also reveal new information about innate immunity in the root. The spatial and temporal information for flg22-induced signaling was achieved using the fluorescent ROS sensor, DCF (Halliwell & Whiteman, 2004a;Tyburski et al, 2009;Chapman & Muday, 2021). Confocal micrographs showed peak fluorescence in the elongation zone (EZ) (Fig 1A), which is consistent with a previous study that demonstrated that the EZ is especially sensitive to flg22 (Millet et al, 2010).…”

May the dark be with roots: a perspective on how root illumination may bias in vitro research on plant–environment interactions

“…ROS‐dependent root hair formation, meristematic activity and lateral root development are additionally regulated by flavonols (Silva‐Navas et al ., 2016; Chapman & Muday, 2020; Gayomba & Muday, 2020). Roots exposed to light can also accumulate high levels of flavonols (Silva‐Navas et al ., 2016; Qu et al ., 2017).…”

Anthocyanins in photoprotection: knowing the actors in play to solve this complex ecophysiological issue

“…Early studies performed on flavonoid‐deficient mutants offered conclusive evidence of their ability to provide ultraviolet (UV)‐B photoprotection (Li et al ., 1993; Lois & Buchanan, 1994; Bieza & Lois, 2001). Their significance as reactive oxygen species (ROS) scavengers and modulators of various developmental processes mediated by ROS and phytohormone signaling (depending on light stress severity) has also been recently ascertained (Hernandez et al ., 2009; Agati & Tattini, 2010; Watkins et al ., 2017; Muhelemann et al ., 2018; Chapman et al ., 2019; Agati et al ., 2020; Chapman & Muday, 2021). Anthocyanins, differently from flavonoids, have the peculiar capacity of absorbing wavelengths over a wider range, from UV‐B to red, of the solar spectrum (Lopes da Silva et al ., 2007; Skaar et al ., 2014; Aguilar & Hernández‐Brenes, 2015; Nichelmann & Bilger, 2017; Gould et al ., 2018), and exclusively accumulate in the vacuoles of epidermal and/or subepidermal cells in red leaves (Hughes & Smith, 2007; Hughes et al ., 2007; Hughes, 2011; Boldt et al ., 2014; Tattini et al ., 2017).…”