WUSCHEL triggers innate antiviral immunity in plant stem cells

Abstract

Stem cells in plants constantly supply daughter cells to form new organs and are expected to safeguard the integrity of the cells from biological invasion. Here, we show how stem cells of the Arabidopsis shoot apical meristem and their nascent daughter cells suppress infection by cucumber mosaic virus (CMV). The stem cell regulator WUSCHEL responds to CMV infection and represses virus accumulation in the meristem central and peripheral zones. WUSCHEL inhibits viral protein synthesis by repressing the expression of plant S-adenosyl-l-methionine–dependent methyltransferases, which are involved in ribosomal RNA processing and ribosome stability. Our results reveal a conserved strategy in plants to protect stem cells against viral intrusion and provide a molecular basis for WUSCHEL-mediated broad-spectrum innate antiviral immunity in plants.

PAMP-triggered Genetic Reprogramming Involves Widespread Alternative Transcription Initiation and an Immediate Transcription Factor Wave

“…The vascular stem cell-specific transcription factor WUSCHEL-like homeobox 4 (WOX4, At1g46480) (Etchells et al 2013; Suer et al 2011) may also belong to the category of growth-arresting factors, although it has not previously been associated with immunity or other stress responses. This is because of the recent finding that in stem cells of the shoot apical meristem, the founding WOX family member WUSCHEL (WUS) acts to repress translation globally via repression of ribosomal rRNA processing (Wu et al 2020). Another stem cell transcription factor, KNAT1/BP (At4g08150) was also part of C5, although it is unclear whether its activities are related to repression of growth.…”

Innate antiviral immunity in plant apical meristem explained

“…Jusqu'à présent ce phénomène restait inexpliqué. Il vient d'être établi qu'un gène connu depuis près de 25 ans, WUSCHEL (WUS), en était responsable et son mécanisme d'action a été élucidé [2].…”

“…Son expression est localisée dans les quelques cellules de la zone centrale du méristème [4]. Wu et al [2] ont remarqué que la présence du virus CMV (virus de la mosaïque du concombre) était limitée aux parties de la plante situées sous la zone d'expression de WUS et cela les a mis sur la piste de ce gène. En utilisant des mutants dans lesquels l'expression de WUS est abolie ou sur-exprimée de façon constitutive ou inductible par la dexaméthasone, ils ont très élégamment démontré que WUS était responsable de l'immunité antivirale.…”

“…So far, this phenomenon remained unexplained. Recently, a gene known for 25 years, WUSCHEL (WUS), has been shown to be responsible for this trait and the underlying mechanisms elucidated [2].…”

“…Its expression is restricted to the few cells of the central zone of the shoot apical meristem [4]. Wu et al [2] have observed that, following infection with the Cucumber Mosaïc Virus (CMV), the virus did not accumulate in the meristem but in the underneath tissues, suggesting a role for WUS in limiting infection. Using knock-out and over-expressing, either constitutive or dexamethasone-inducible, wus mutants, they nicely demonstrated that WUS is responsible for this antiviral immunity.…”