Salicylic acid promotes quiescent center cell division through ROS accumulation and down‐regulation of PLT1, PLT2, and WOX5

Abstract

Salicylic acid (SA) plays a crucial role in plant immunity. However, its function in plant development is poorly understood. The quiescent center (QC), which maintains columella stem cells (CSCs) in the root apical meristem and typically exhibits low levels of cell division, is critical for root growth and development. Here, we show that the Arabidopsis thaliana SA overaccumulation mutant constitutively activated cell death 1 (cad1), which exhibits increased cell division in the QC, is rescued by additional mutations in genes encoding the SA biosynthetic enzyme SALICYLIC ACID INDUCTION DEFFICIENT2 (SID2) or the SA receptor NONEXPRESSER OF PR GENES1 (NPR1), indicating that QC cell division in the cad1 mutant is promoted by the NPR1‐dependent SA signaling pathway. The application of exogenous SA also promoted QC cell division in wild‐type plants in a dose‐dependent manner and largely suppressed the expression of genes involved in QC maintenance, including those encoding the APETALA2 (AP2) transcription factors PLETHORA1 (PLT1) and PLT2, as well as the homeodomain transcription factor WUSCHEL‐RELATED HOMEOBOX5 (WOX5). Moreover, we showed that SA promotes reactive oxygen species (ROS) production, which is necessary for the QC cell division phenotype in the cad1 mutant. These results provide insight into the function of SA in QC maintenance.

Hormonal Regulation of Stem Cell Proliferation at the Arabidopsis thaliana Root Stem Cell Niche

“…It remains to be determined if this redox regulation also occurs in Arabidopsis . Experiments in Arabidopsis indicate that SA-induced QC cell divisions are accompanied by an increase in ROS levels and a decrease in auxin signaling in the QC cells ( Wang et al, 2020 ), thus suggesting the existence of a mechanism similar to the one described in maize roots.…”

“…In Arabidopsis , root growth is not compromised by genetic perturbations that result in alterations in the division patterns of the QC cells, suggesting that low division rate of the QC cells is not strictly necessary for the function and the organization of the root meristem under optimal growth conditions ( Vanstraelen et al, 2009 ; González-García et al, 2011 ; Cruz-Ramírez et al, 2013 ; Savina et al, 2020 ; Wang et al, 2020 ). The division of the QC cells has been shown to increase in frequency in older Arabidopsis seedlings ( Timilsina et al, 2019 ), and it can also be actively modulated to cope with the current needs of the root.…”

“…Interestingly, this phenotype is accompanied by a reduction in the expression of the transcription factors SCR and SHR ( Yu et al, 2016 ). Salicylic acid (SA) is a hormone that plays an important role in plant defense, and it induces QC cell divisions in a dose-dependent manner ( Wang et al, 2020 ). The SA-induced cell divisions are mediated by an increase in ROS levels the RAM and a downregulation of PLT1 , PLT2 , and WOX5 in the QC cells ( Wang et al, 2020 ).…”

“…Salicylic acid (SA) is a hormone that plays an important role in plant defense, and it induces QC cell divisions in a dose-dependent manner ( Wang et al, 2020 ). The SA-induced cell divisions are mediated by an increase in ROS levels the RAM and a downregulation of PLT1 , PLT2 , and WOX5 in the QC cells ( Wang et al, 2020 ). It was also previously shown that increased ROS levels cause a downregulation of PLT genes, a higher expression of ERF115 , among other factors ( Kong et al, 2018 ).…”

Plant abiotic stress: New insights into the factors that activate and modulate plant responses

“…Root architecture and root growth affect plant tolerance to multiple stresses, particularly drought and nutrient deficiency. An intriguing study by Wang et al (2021) examines the function of salicylic acid (SA), a key hormone for plant immunity, in maintenance of the root quiescent center (QC), finding that SA promotes ROS production and cell division in the QC. Moreover, Su et al (2021) reveal that SUCROSE NON‐FERMENTING kinases 2 function downstream of ABA to modulate the activity of the nitrate transceptor NITRATE TRANSPORTER1.1 and thus root growth under nitrogen deficiency, suggesting that ABA signaling has a cross‐talk with nitrate uptaking in plants.…”