STOP2 Activates Transcription of Several Genes for Al- and Low pH-Tolerance that Are Regulated by STOP1 in Arabidopsis

Abstract

The zinc-finger protein STOP1 (sensitive to proton rhizotoxicity 1) regulates transcription of multiple genes critical for tolerance to aluminum (Al) and low pH in Arabidopsis. We evaluated the contributions of genes that are suppressed in the stop1 mutant to Al- and low pH-tolerance using T-DNA-inserted disruptants, and transgenic stop1 mutants expressing each of the suppressed genes. STOP2, a STOP1 homolog, partially recovered Al- and low pH-tolerance by recovering the expression of genes regulated by STOP1. Growth and root tip viability under proton stress were partially rescued in the STOP2-complemented line. STOP2 localized in the nucleus and regulated transcription of two genes (PGIP1 and PGIP2) associated with cell wall stabilization at low pH. GUS assays revealed that STOP1 and STOP2 showed similar cellular expression in the root. However, the expression level of STOP2 was much lower than that of STOP1. In a STOP1 promoter::STOP2-complemented line, Al tolerance was slightly recovered, concomitant with the recovery of expression of ALS3 (aluminum sensitive 3) and AtMATE (Arabidopsis thaliana multidrug and toxic compound extrusion), while the expression of AtALMT1 (aluminum-activated malate transporter 1) was not recovered. These analyses indicated that STOP2 is a physiologically minor isoform of STOP1, but it can activate expression of some genes regulated by STOP1.

Transcriptome Analysis of Al-Induced Genes in Buckwheat (Fagopyrum esculentum Moench) Root Apex: New Insight into Al Toxicity and Resistance Mechanisms in an Al Accumulating Species

“…Furthermore, WRKY46 and CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR2 have been demonstrated to act as transcriptional repressor and activator of AtALMT1 expression, respectively (Ding et al, 2013; Tokizawa et al, 2015). STOP2, a STOP1 homolog, can partially restore Al- and low pH-tolerance by recovering the expression of genes regulated by STOP1 (Kobayashi et al, 2014). Here, we identified not only these known TF homologs such as STOP1, STOP2, CAMTA, WRKY, and ASR, but a number of novel TFs including ABI3VP1, bHLH, C2H2-GATA, C3H, HB, HSF, MADS, MYB and NAC, some of which may be involved in Al resistance and/or Al toxicity (Supplementary Table S2 and Table 2 ).…”

Plant Hormones under Challenging Environmental Factors

“…Therefore, we can suggest that ethylene and auxin interact to inhibit the main root elongation and stimulate root hair formation for plants exposed to a low pH stress. The STOP 1 is a transcription factor, which is regulated by the expression of al uminum-activated m alate t ransporter 1 (ALMT1) (Kobayashi et al 2014 ). Moreover, several studies dealing with the phytohormonal responses to acid soil were unable to separate the effects caused by Al toxicity and a low pH stress.…”

The roles of STOP1-like transcription factors in aluminum and proton tolerance

“…18,21 Either AtSTOP1 and AtSTOP2 in Arabidopsis or OsART1 in rice is constitutively expressed, 14,16,17 thus Al or H C regulates them posttranslationally, e.g. direct activation of protein activity.…”

“…13,15 In addition to regulate Al tolerance genes, AtSTOP1 also regulates a series of potential H C tolerance genes, including genes encoding CBL-interaction protein kinase 23, Polygalacturonase inhibiting protein 1, Glutamate dehydrogenase 1, AtSTOP2 and so on. 13,16 Thus, the identification of AtSTOP1 first links Al tolerance and H C tolerance together at molecular level. An AtSTOP1 homolog in rice, OsART1, was identified using a mutant-screening approach.…”

“…19,20 Nonetheless, AtSTOP2-RNAi lines did not display altered Al-and proton-sensitivity, but showed significant proton tolerance in Atstop1 complemented lines. 16 One possible reason is functional redundancy between AtSTOP2 and AtSTOP1, since AtSTOP2 functions in downstream of AtSTOP1. There is a similar case in rice that loss-of-function mutant of OsART1 did not show any sensitivity to proton.…”