PLETHORA-WOX5 interaction and subnuclear localisation controlArabidopsisroot stem cell maintenance

Abstract

Total word count: 7260 20 of the PLT-WOX5 complexes to NBs, possibly by liquid-liquid phase separation, plays an 38 important role during determination of CSC fate. 39 differentiation 6,7 . WOX5 also represses QC divisions, maintaining the quiescence of the QC by 65 repressing CYCLIN D (CYCD) activity within the QC 8 . The auxin-induced PLTs form a clade 66 of six TFs, and act as master regulators of root development, as multiple plt mutants fail to 67 develop functional RAMs 5,9,10 . PLT1, 2, 3 and 4 are expressed mainly in and around the QC 68 and form an instructive gradient, which is required for maintaining the balance of stem cell fate 69 and differentiation. This PLT gradient is also necessary for separating auxin responses in the 70 SCN and for the correct positioning of the QC and the expression of QC markers 5,9,10 . 71Genetically, WOX5 and PLT1 were shown to play an interconnected role in auxin-regulated 72 CSC fate, whereas PLT1 and PLT3 were found to positively regulate WOX5 expression 11,12 . 73 Although the implication of PLTs and WOX5 in controlling stem cell regulation and 74 maintenance in the Arabidopsis RAM is well established and genetic evidence for cross 75 regulation exists, the underlying molecular mechanisms remain largely elusive. Here, we show 76 that the mutual regulation of expression, but also the ability of PLTs, especially PLT3, to recruit 77 WOX5 to NBs in CSCs controls stem cell homeostasis in the Arabidopsis RAM. We propose 78 a model in which the differential PLT/WOX5 complexes depending on subnuclear localisation 79 regulate stem cell fate in the RAM, possibly by phase separation of PLT3 to NBs. 80Suppl. Table 7). In the plt2 and plt3 single mutants, the frequency of roots lacking a CSC layer 130 increases to above 30 % (36 % and 32 %, respectively), and in the plt2, plt3 double mutant to 131 41% (see Fig. 3c,d,e,i, Suppl. Table 7). Interestingly, the wox5, plt3 double mutant as well as 132 the wox5, plt2, plt3 triple mutant show a frequency of differentiated CSCs comparable to the 133 wox5 single mutant (71 % and 77 %, respectively) ( Fig. 3g,h,i, Suppl. Table 7). This data 134suggests that PLTs and WOX5 may act together in the same pathway to maintain CSC 135 homeostasis, as there is no additive effect observable in the multiple mutant roots. To analyse 136

Precise transcriptional control of cellular quiescence by BRAVO/WOX5 complex in Arabidopsis roots

“…WOX5 self-repression can also involve a negative feedback where WOX5 activates a repressor or represses an activator, among other possibilities. In this context, control of auxin-ARF and auxin-IAA (Tian et al, 2014b) as well as the PLETHORA genes (Burkart et al, 2019) were all shown to involve negative feedbacks with WOX5. WOX5 induction of BRAVO expression could be as well through a downstream target of WOX5.…”

Interkingdom Comparison of Threonine Metabolism for Stem Cell Maintenance in Plants and Animals

“…PLT proteins form a gradient along the transit-amplifying domain of the RAM with a maximum in the QC ( Galinha et al, 2007 ; Mähönen et al, 2014 ) where PLT proteins restrict WOX5 expression domain to the QC ( Santuari et al, 2016 ; Burkart et al, 2019 ). WOX5 promotes cell quiescence by direct transcriptional repression of CYCLIN D ( CYCD ; Forzani et al, 2014 ).…”

“…WOX5 promotes cell quiescence by direct transcriptional repression of CYCLIN D ( CYCD ; Forzani et al, 2014 ). Moreover, WOX5 promotes PLT expression ( Ding and Friml, 2010 ; Burkart et al, 2019 ), creating a transcriptional feedback loop that reinforces quiescence of the QC cells. PLT1 and PLT3 transcriptionally activate WOX5 through binding to its promoter and, at the same time, PLT proteins interact indirectly with SCR, through class I members of the Teosinte-branched Cycloidea PCNA (TCP) proteins ( Shimotohno et al, 2018 ).…”

A blast from the past: Understanding stem cell specification in plant roots using laser ablation

“…Recent work has shown that besides transcriptional regulation, these transcription factors also form protein complexes that localise to nuclear bodies in the columella stem cells, which could serve an important role in CSC fate determination (Burkart et al, 2022). Besides PLT, WOX5 expression is also dependent on the BRASSI-NOSTEROIDS AT VASCULAR AND ORGANIZING CENTER R2R3-MYB transcription factor (BRAVO), which has been suggested to act through the formation of a hetero dimer complex and through subsequent disruption of the WOX5 negative feedback on itself (Betegón-Putze et al, 2021;Mercadal et al, 2022).…”