Raw data for Xyloglucan deficiency leads to a reduction in turgor pressure and changes in cell wall properties affecting early seedling establishment

Xyloglucan is believed to play a significant role in cell wall mechanics of dicot plants.
Surprisingly, Arabidopsis plants defective in xyloglucan biosynthesis exhibit nearly
normal growth and development. We investigated a mutant line, cslc-Δ5, lacking
activity in all five Arabidopsis CSLC genes responsible for xyloglucan backbone
biosynthesis. We observed that this xyloglucandeficient line exhibited reduced
cellulose crystallinity and increased pectin levels, suggesting the existence of feedback
mechanisms that regulate wall composition to compensate for the absence of
xyloglucan. These alterations in cell wall composition in the xyloglucan-absent plants
were further linked to a decrease in cell wall elasticity and rupture stress, as observed
through atomic force microscopy and extensometer-based techniques. This raised
questions about how plants with such modified cell wall properties can maintain normal
growth. Our investigation revealed two key factors contributing to this phenomenon.
Firstly, measurements of turgor pressure, a primary driver of plant growth, revealed
that cslc-Δ5 plants have reduced turgor, preventing the compromised walls from
bursting while still allowing growth to occur. Secondly, we discovered the conservation
of elastic asymmetry (ratio of axial to transverse wall elasticity) in the mutant,
suggesting an additional mechanism contributing to the maintenance of normal growth.
This novel feedback mechanism between cell wall composition and mechanical
properties, coupled with turgor pressure regulation, plays a central role in the control of
plant growth and is critical for seedling establishment in a mechanically challenging
environment by affecting shoot emergence and root penetration.