GDSL-domain containing proteins mediate suberin biosynthesis and degradation, enabling developmental plasticity of the endodermis during lateral root emergence

Abstract

Roots anchor plants and deliver water and nutrients from the soil. The root endodermis provides the crucial extracellular diffusion barrier by setting up a supracellular network of lignified cell walls, called Casparian strips, supported by a subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, formation of suberin lamellae was demonstrated to be dynamic, facilitating adaptation to different soil conditions. Plants shape their root system through the regulated formation of lateral roots emerging from within the endodermis, requiring local breaking and re-sealing of the endodermal diffusion barriers. Here, we show that differentiated endodermal cells have a distinct auxin-mediated transcriptional response that regulates cell wall remodelling. Based on this data set we identify a set of GDSL-lipases that are essential for suberin formation. Moreover, we find that another set of GDSLlipases mediates suberin degradation, which enables the developmental plasticity of the endodermis required for normal lateral root emergence.

Suberin plasticity to developmental and exogenous cues is regulated by a set of MYB transcription factors

“…In order to verify if this conditional induction of MYB41 was able to induce the rest of the suberin biosynthetic pathway, we measured the transcript levels of suberin biosynthesis genes and the other MYBs of interest. A short treatment of 3h with estradiol was enough to strongly induce MYB41 expression as well as nearly all the biosynthetic enzymes, including the recently characterized GELPs ( GDSL-type Esterase/Lipases ) (42) coding for enzymes involved in the polymerization of suberin monomers in the cell wall (Fig. 2G).…”

“…For example, the gpat5 mutant lacking a key enzyme for suberin biosynthesis displays only a 30% reduction of suberin monomer accumulating in its roots (53). To our knowledge, the only genotypes displaying a range of reduction comparable to the quad-myb is the quintuple gelp22-38-49-51-96 mutant (affected in suberin polymerization in the cell wall), and the ELTP::MYB4 line (where inhibition of the phenylpropanoid pathway in the endodermis leads to suberin detachment), both displaying an 85% reduction of suberin monomers in roots (42, 54). We are therefore confident that MYB41, MYB53, MYB92 and MYB93 form the core regulating machinery controlling suberization in unstressed conditions.…”

“…For endodermal specific estradiol inducible MYB41 expression ( CASP1xve::MYB41-mVenus) , the entry vectors containing the inducible CASP1 promoter pEN-L4-CASP1xve-R1 (63) was recombined with pDONR221_L1-MYB41nostop-L2 and pEN-R2-mVenus +stop-L3 into the destination vector pFG7m34GW. Cloning of vectors for CRISPR/Cas9 was done as previously described in (42, 64). sgRNA for spCas9 were designed using webtools – CRISPR-P 2.0 design tool (http://crispr.hzau.edu.cn/CRISPR2/) (65) and Benchling (https://www.benchling.com).…”

“…After fluorescent seed selection in T1, non-fluorescent seeds in the T2 generation (indicating a segregation of the vector backbone containing the Cas9 cassette) were used to identify the mutations. Primary screening of mutants was done using High-Resolution Melting (HRM) curve analysis as previously described in (42). Candidates from HRM analysis were further confirmed for the mutations by sequencing of PCR-amplified genomic regions.…”

Mini Review: Transport of Hydrophobic Polymers Into the Plant Apoplast

“…Currently, there is no proposed role of monolignols and fatty alcohols (not shown) in suberin, but theoretically, they could behave as glycerol molecules (i.e., hydroxy groups ester bond with the carboxy groups of the fatty acids). An increasing number of studies suggest that GDSL family transacylases contribute to suberin polymerization ( Lashbrooke et al, 2016 ; Ursache et al, 2020 ). Wiggle lines indicate unspecified ester bonds.…”