Actin Isovariant ACT7 Modulates Root Thermomorphogenesis by Altering Intracellular Auxin Homeostasis

Abstract

High temperature stress is one of the most threatening abiotic stresses for plants limiting the crop productivity world-wide. Altered developmental responses of plants to moderate-high temperature has been shown to be linked to the intracellular auxin homeostasis regulated by both auxin biosynthesis and transport. Trafficking of the auxin carrier proteins plays a major role in maintaining the cellular auxin homeostasis. The intracellular trafficking largely relies on the cytoskeletal component, actin, which provides track for vesicle movement. Different classes of actin and the isovariants function in regulating various stages of plant development. Although high temperature alters the intracellular trafficking, the role of actin in this process remains obscure. Using isovariant specific vegetative class actin mutants, here we demonstrate that ACTIN 7 (ACT7) isovariant plays an important role in regulating the moderate-high temperature response in Arabidopsis root. Loss of ACT7, but not ACT8 resulted in increased inhibition of root elongation under prolonged moderate-high temperature. Consistently, kinematic analysis revealed a drastic reduction in cell production rate and cell elongation in act7-4 mutant under high temperature. Quantification of actin dynamicity reveals that prolonged moderate-high temperature modulates bundling along with orientation and parallelness of filamentous actin in act7-4 mutant. The hypersensitive response of act7-4 mutant was found to be linked to the altered intracellular auxin distribution, resulted from the reduced abundance of PIN-FORMED PIN1 and PIN2 efflux carriers. Collectively, these results suggest that vegetative class actin isovariant, ACT7 modulates the long-term moderate-high temperature response in Arabidopsis root.

Actin isovariant ACT7 controls root meristem development in Arabidopsis through modulating auxin and ethylene responses

“…All the experiments were repeated at least three or four times. Actin quantification was performed using ImageJ software (http://rsb.info.nih.gov/ij/) as described earlier (Higaki et al,2010, Takashi et al, 2014, Parveen and Rahman, 2021). Before measurements of actin parameters, the confocal images were skeletonized using the ImageJ plug-in LPX LineExtract (Ueda et al, 2010).…”

“…For instance, among three vegetative actin, ACT7 had been shown to be preferentially and strongly expressed in all young and developing vegetative tissue including root meristem, and ACT7 expression is strongly altered by plant hormone auxin and several external stimuli (McDowell et al, 1996a). It had also been shown that ACT7 regulates germination, root growth, epidermal cell specification, root architecture, and root thermomorphogenesis (Gilliland et al, 2003; Kandasamy et al, 2009, Parveen and Rahman, 2021). On the other hand, ACT2 and ACT8 regulate bulge site selection, root hair growth, and leaf morphology (Ringli et al, 2002; Nishimura et al, 2003; Kandasamy et al, 2009; Vaškebová et al, 2018).…”

An apple somatic mutation of delayed fruit maturation date is primarily caused by a retrotransposon insertion‐associated large deletion

“…More importantly, ACT7 is expressed strongly in young seedlings and developing organs, and is the only actin encoding gene that is responsive to plant hormones [auxin, cytokinin, abscisic acid (ABA)] and external stimuli (light, wounding; McDowell, An, et al., 1996). ACT7 is also required for callus formation (Kandasamy et al., 2001), clustering of chloroplasts around the nucleus before cell division (Sheahan et al., 2020), and root response to moderate–high temperature (Parveen & Rahman, 2021).…”

A Selection of Reliable Reference Genes for Gene Expression Analysis in the Female and Male Flowers of Salix suchowensis

“…According to the four algorithms and the comprehensive evaluation of RefFinder, ACT , and DnaJ were the most stable reference genes in both the male and female flowers of S. suchowensis at different developmental stages. ACT is actin and one of the three main components of the cytoskeleton [ 36 ]. The growth of pollen tubes in male flowers requires the coordination of the cytoskeletal dynamics and apical secretion [ 37 ].…”