Phosphoethanolamine N‐methyltransferase 1 contributes to maintenance of root apical meristem by affecting ROS and auxin‐regulated cell differentiation in Arabidopsis

Abstract

Summary The continuous growth of roots requires the balance between cell division and differentiation. Reactive oxygen species (ROS) and auxin are important regulators of root development by affecting cell division and differentiation. The mechanism controlling the coordination of cell division and differentiation is not well understood. Using a forward genetic screen, we isolated a mutant, defective primary root 2 (dpr2), defective in root apical meristem (RAM) maintenance. The DPR2 gene encodes phosphoethanolamine N‐methyltransferase 1 (PEAMT1) that catalyzes phosphocholine biosynthesis in Arabidopsis. We characterized the primary root phenotypes of dpr2 using various marker lines, using histochemical and pharmacological analysis to probe early root development. Loss‐of‐function of DPR2/PEAMT1 resulted in RAM consumption by affecting root stem cell niche, division zone, elongation and differentiation zone (EDZ). PIN‐FORMED (PIN) protein abundance, PIN2 polar distribution and general endocytosis were impaired in the root tip of dpr2. Excess hydrogen peroxide and auxin accumulate in the EDZ of dpr2, leading to RAM consumption by accelerating cell differentiation. Suppression of ROS over‐accumulation or inhibition of auxin signalling partially prevent RAM differentiation in dpr2 after choline starvation. Taken together, we conclude that the EDZ of the root tip is most sensitive to choline shortage, leading to RAM consumption through an ROS–auxin regulation module.

Engineered Aim-Based Selective Autophagy to Degrade Proteins and Organelles

“…Arabidopsis thaliana ecotype Col-0 was used as the wild-type control; the defective primary root 2 (dpr2) mutant 26 , transgenic lines PEAMT1-GFP 26 , and BIN2-GFP 30 were described previously. All Arabidopsis seeds were surface sterilized using vapor phase The free GFP (or mCherry)-release assays were conducted as previously described 36 .…”

“…The root lengths of transgenes in the PEAMT1-GFP dpr2 background were measured according to the method described previously 26 . Briefly, seeds were stratified at 4°C in distilled water for at least 6 d after surface sterilization, then germinated on 1/2 MS solid medium and grown vertically.…”

“…Having confirmed that AIM-GBP-mCherry could mediate the autophagic degradation of GFP fusion proteins when expressed transiently, we next asked whether this approach could be applied to stably expressed GFP fusions. For this purpose, we chose the Arabidopsis mutant defective primary root 2 (dpr2 or peamt1) carrying the rescue transgene PEAMT1-GFP 26 . PEAMT1 encodes phosphoethanolamine Nmethyltransferase 1, an enzyme essential for the biosynthesis of the phospholipid phosphatidylcholine.…”

“…PEAMT1 encodes phosphoethanolamine Nmethyltransferase 1, an enzyme essential for the biosynthesis of the phospholipid phosphatidylcholine. The loss of PEAMT1 affected the ROS-and auxin-regulated cell differentiation in the root apical meristem and caused a short primary root phenotype 26 .…”

Initiation and maintenance of plant stem cells in root and shoot apical meristems

“…The DPR2 gene encodes phosphoethanolamine N-methyltransferase 1 (PEAMT1) that catalyzes phosphocholine biosynthesis in Arabidopsis. Loss-of-function of DPR2/PEAMT1 resulted in RAM consumption by affecting root stem cell niche, division zone, and elongation and differentiation zone (EDZ), which were result from the altered ROS and auxin homeostasis (Zou et al 2019). ROS signaling could be also interpreted through ROS-responsive factors such as ERF transcription factors ERF115, ERF114, and ERF109 to maintain root SCN identity (Kong et al 2018).…”