Transcriptional induction of cell wall remodelling genes is coupled to microtubule-driven growth isotropy at the shoot apex in Arabidopsis

Abstract

The shoot apical meristem of higher plants continuously generates new tissues and organs through complex changes in growth rates and directions of its individual cells. Cell growth, which is driven by turgor pressure, largely depends on the cell walls, which allow cell expansion through synthesis and structural changes. A previous study revealed a major contribution of wall isotropy in organ emergence, through the disorganization of cortical microtubules. We show here that this disorganization is coupled with the transcriptional control of genes involved in wall remodelling. Some of these genes are induced when microtubules are disorganized and cells shift to isotropic growth. Mechanical modelling shows that this coupling has the potential to compensate for reduced cell expansion rates induced by the shift to isotropic growth. Reciprocally cell wall loosening induced by different treatments or altered cell wall composition promotes a disruption of microtubule alignment. Our data thus indicate the existence of a regulatory module activated during organ outgrowth, linking microtubule arrangements to cell wall remodelling.

From spatio-temporal morphogenetic gradients to rhythmic patterning at the shoot apex

“…6). This is coherent with genetic and expression data (Extended Data Table 1) 11,35 . Both YUC1 and YUC4 are expressed at the L1 layer on the lateral sides of the SAM/flower boundary from P3 for YUC4 and in P4 for YUC1 11 (Fig.…”

“…Error values equal to 0 denote identical maps. The lowest error values with rotated maps (blue points) were globally found between the 10h map and the 0h map close to a 137° rotation, validating that the extrapolation heuristic of placing P1 at T=0h right after P0 at T=10h is indeed the most consistent way to extend a sequence in time 35 .…”

Xyloglucan homeostasis and microtubule dynamics synergistically maintain meristem geometry and robustness of phyllotaxis in Arabidopsis

“…The precise function of XyGs in development has remained controversial. In a previous study, we showed that genes encoding XyGs modifying enzymes like the XTHs, are highly expressed and show specific expression patterns at the meristem suggesting an important role for XyGs during morphogenesis (Armezzani et al, 2018). Here we explored the role of these components further, and show that specific XyG residues accumulate in different functional domains of the SAM.…”

“…There are several indications that they play an important role at the SAM. Genes encoding xyloglucan endotransglucosylases/hydrolases (XTH), involved in remodeling the XyGs, are very abundantly expressed at the shoot apical meristem (Armezzani et al, 2018). Moreover, Xiao et al (2016) revealed that loss of xyloglucan in the xxt1/xxt2 mutant affects cell wall integrity, the stability of the microtubule cytoskeleton and the production and patterning of cellulose in primary cell walls in hypocotyls.…”

ArabidopsisXTH4andXTH9contribute to wood cell expansion and secondary wall formation

“…Although we have seen changes in expression of several genes encoding microtubule associated proteins (MAPs) that play essential role in MT dynamics, these changes may be due to overall secondary wall induction in the stems of mutants, as they paralleled expression of secondary wall CesAs ( Figure 8 B, C ). There are other reports suggesting a possible coupling between XTHs or XG, cortical microtubules and cellulose biosynthesis (Takeda et al, 2002; Sasidharan et al, 2014; Xiao et al, 2016; Armezzani et al, 2018), but it is unclear how this coupling mechanistically occurs.…”