ROS and calcium oscillations are required for polarized root hair growth

Abstract

Root hairs are filamentous extensions from epidermis of plant roots with growth limited to the apical dome. Cell expansion undergoes tightly regulated processes, including the coordination between cell wall loosening and cell wall crosslinking, to form the final shape and size. Tip-focused gradients and oscillations of reactive oxygen species (ROS) together with calcium ions (Ca 2+ ) as indispensable regulated mechanisms control rapid and polarized elongation of root hair cells. ROS homeostasis mediated by plasma membrane-localized NADPH oxidases, known as respiratory burst oxidase homologues (RBOHs), and class III cell wall peroxidases (PRXs), modulates cell wall properties during cell expansion. The expression levels of RBOHC , an NADPH oxidase that produces ROS, and class III PRXs are directly upregulated by ROOT HAIR DEFECTIVE SIX-LIKE 4 ( RSL4 ), encoding a basic-helix-loop-helix (bHLH) transcription factor, to modulate root hair elongation. Cyclic nucleotide-gated channels (CNGCs), as central regulators of Ca 2+ oscillations, also regulate root hair extension. Here, we review how the gradients and oscillations of Ca 2+ and ROS interact to promote the expansion of root hair cells.

A cotton APS REDUCTASE represses root hair elongation via sulfur assimilation and hydrogen peroxide‐mediated cell wall damage

“…These proteins also show some crosstalk with different phytohormones (Masucci and Schiefelbein 1994, 1996, Kubenova et al 2022, Sun et al 2022). Additionally, abnormal ROS accumulation in RHs triggers either exacerbated growth or cell bursting, reinforcing the notion that an apoplastic and cytosol ROS‐homeostasis is required to modulate RH initiation and cell elongation by affecting cell wall properties (Orman‐Ligeza et al 2016, Pacheco et al 2022, Zhang et al 2022). The cell wall, a dynamic structure, determines the fate and shape of epidermal cells and root hairs.…”

“…RHs are elongated several hundred‐fold of their original dimensions in a short‐term period, and their differentiation and elongation rates are determined by both cell‐intrinsic factors and external environment signals (Bruex et al 2012, Chang et al 2021, Fedoreyeva et al 2022, Li et al 2022). The distinctive morphological characteristic and development profile of RHs make them important regulators of mineral and water uptake, especially in response to nutrient deficiencies such as phosphorus, iron, and calcium (Bates and Lynch 1996, Kohli et al 2022, Xue et al 2022, Ying and Scheible 2022, Zhang et al 2022). Genetic and molecular approaches have identified several hormones, including auxin, ethylene, jasmonic acid (JA), and abscisic acid (ABA), as important factors in RH development (Lee and Cho 2013, Rymen et al 2017, Qiu et al 2021, Li et al 2022, Martin et al 2022).…”

Bio‐positive effects of ionizing radiation on pollen: The role of ROS

“…ROS can be toxic to cells, however, they also play regulatory roles in numerous physiological processes, for example, in cell growth, cell division, differentiation and development, as well as responses to biotic and abiotic stimuli (Czarnocka and Karpinski, 2018; Foyer and Noctor, 2016). It has been demonstrated that ROS act as signalling molecules in the regulation of processes like pollen germination and tip growth of pollen tubes (Liu et al, 2009; Maksimov et al, 2018; Pasqualini et al, 2015; Speranza et al, 2012) as well as root hairs (Carol and Dolan, 2006; Carol et al, 2005; Foreman et al, 2003; Zhang et al, 2022). In this connection, ROS are endogenously generated by cellular NADPH oxidases (NOX) (Figure 3) (Cardenas et al, 2006; Foreman et al, 2003; Kaya et al, 2015; Kaya et al, 2014; Kaya et al, 2019; Lassig et al, 2014; Potocky et al, 2007).…”

Review of the Mechanisms by Which Transcription Factors and Exogenous Substances Regulate ROS Metabolism under Abiotic Stress

“…Zhang et al reported that CsRbohD is essential in resistance to cold stress in cucumber. These results suggest that RBOHD and RBOHF act as ROS signal initiators and activate antioxidant systems during plant resistance to salt and cold stress [ 36 ]. Whether RBOH D and E genes expression is regulated by other abiotic stresses and what the roles of other RBOH s are in abiotic stresses may remain to be explored.…”

“…Many studies have shown that exogenous Ca 2+ is beneficial for plants in scavenging ROS [ 178 , 179 , 180 ]. In general, exogenous calcium stimulates the production of ROS, which acts as a signal to activate the ROS scavenging system in plants to avoid oxidative damage [ 36 ]. Calcium ions enhance RBOH activity and promote the production of plasma membrane ROS, which act as a signal to activate antioxidant enzymes (i.e., POD, CAT and SOD) and the antioxidant system of the AsA-GSH cycle in potato tuber [ 181 ].…”