The role of auxin transporters and receptors in adventitious rooting of Arabidopsis thaliana pre-etiolated flooded seedlings

Abstract

Adventitious roots (ARs) form from above-ground organs, and auxins are major regulators of AR development. TIR1/AFB F-box proteins act as well-established auxin receptors. Auxin transport involves the PINFORMED (PIN) auxin efflux carriers and AUXIN RESISTANT 1/LIKE AUX1 (AUX1/LAX1) influx carriers. To further elucidate the basis of AR development, we investigated the participation of these proteins and phosphorylation of PINs during adventitious rooting in hypocotyls of pre-etiolated flooded Arabidopsis thaliana seedlings. Mutant and GUS localization studies indicated that AFB2 is important in AR development. AUX1 loss-of-function reduced AR numbers, which could not be reversed by exogenous auxin. Single mutations in LAX1, LAX2 and LAX3 had no negative impact on AR development and the first and last mutations even promoted it. Double and triple mutants of AUX1, LAX1, LAX2 and LAX3 significantly reduced rooting, which was reversed by exogenous auxin. AUX1 was essential in AR establishment, with LAX3 apparently acting in conjunction. Proper phosphorylation of PINs by PID, WAG1 and WAG2 and auxin transport direction were equally essential for AR establishment. PIN1, AUX1 and AFB2 (overexpression) and LAX1, LAX3, PIN4 and PIN7 (downregulation) emerged as potential targets for genetic manipulation aiming at improving AR development.

An auxin‐mediated regulatory framework for wound‐induced adventitious root formation in tomato shoot explants

“…Interestingly, the chemical inhibition of the auxin influx carriers AUX1/LAX by 2‐NOA allowed the formation of callus‐like tissue at the basal hypocotyl (resembling NAA‐treated hypocotyl explants), which were severely delayed in AR formation. Indeed, in Arabidopsis hypocotyls, the activity of AUX1 is essential for AR initiation (da Costa, Offringa, & Fett‐Neto, 2020), while other LAX members (such as LAX3) are required for AR emergence (Della Rovere et al, 2013, 2015). Consequently, when the new ARs emerged during the expression phase (de Klerk et al, 1999), they acted as active sinks for the basipetal auxin transported from the shoot, limiting the auxin overflow effect observed in the most basal region of the hypocotyl at earlier time‐points.…”

A novel miR167a-OsARF6-OsAUX3 module regulates grain length and weight in rice

“…Auxin transporters of the AUX1/LAX family play an important role in plant growth and development (Habets and Offringa, 2014;Peret et al, 2012). However, in both Arabidopsis and rice, members of the AUX1/LAX family have been reported to contribute mainly to root development (da Costa et al, 2020;Giri et al, 2018;Swarup and Bhosale, 2019;Yu et al, 2015;Zhao et al, 2015). In this study, through forward and reverse genetics, OsAUX3 was found to act as a determinant of GL and GW in rice (Figures 1 and 3).…”

“…AUX1/LAX genes were shown to influence the development of primary roots, lateral roots, and root hairs, as well as root gravitropism (Giri et al, 2018;Swarup and Bhosale, 2019). Moreover, AUX1 and LAX3 are essential for adventitious root establishment (da Costa et al, 2020), and LAX2 regulates vascular patterning in cotyledons (Peret et al, 2012). In rice, the AUX/LAX family comprises five members, among which OsAUX1 and OsAUX3 were shown to regulate root development.…”

Characterization of auxin transporter AUX, PIN and PILS gene families in pineapple and evaluation of expression profiles during reproductive development and under abiotic stresses

“…The PCR products were then constructed into pENTER/ D-TOPO vector (Invitrogen) and then the positive clones were recombined with the destination vector pGWB505 by LR Clonase II enzyme (Invitrogen). The 35S: AcAUX1 recombinant construction was transformed into wild-type and aux1-T (SALK_020355C, Da Costa, Offringa & Fett-Neto, 2020 ) Arabidopsis (Columbia ecotype) using the Agrobacterium- mediated floral dip method. Then, the expression level of AcAUX1 in T1 generation positive seedlings was determined by qPCR.…”