GDSL-domain proteins have key roles in suberin polymerization and degradation

Abstract

Plant roots acquire nutrients and water, while managing interactions with the soil microbiota. Their endodermis provides an extracellular diffusion barrier via a network of lignified cell walls, called Casparian strips, supported by subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, suberin lamellae display plasticity, which is crucial for root adaptative responses in the plant. Despite suberin being a major plant polymer, fundamental aspects of its biosynthesis and turnover have remained obscure. Plants shape their root system via lateral root formation, an auxin-induced process requiring local breaking and re-sealing of endodermal lignin and suberin barriers. Here, we show that differentiated endodermal cells have a specific, auxin-mediated transcriptional response, dominated by cell wall remodelling genes. We identified two sets of auxin-regulated GDSL-lipases. One is required for suberin synthesis, while the other can drive suberin degradation. These enzymes constitute novel core players of suberisation, driving root suberin plasticity.

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

“…When considering shoot weight and root length, quad-myb plants were significantly more reduced compared to WT plants when growing in presence of salt (Fig. 4F) to degrees similar to what was described before for ELTP::CDEF1 and the quintuple gelp22-38-49-51-96 mutant (6, 43). Combined, our results further support the central role of suberin in plant adaptation to the presence of salt.…”

“…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 genes involved in suberin biosynthesis, including the recently characterized GELPs ( GDSL-type Esterase/Lipases ) (43) 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 (55). 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 (43, 56). We are therefore confident that MYB41, MYB53, MYB92 and MYB93 form the core regulating machinery controlling suberization in the endodermis.…”

“…For endodermal specific estradiol inducible MYB41 expression ( CASP1xve::MYB41-mVenus) , the entry vectors containing the inducible CASP1 promoter pEN-L4-CASP1xve-R1 (65) 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 (43, 44, 66). sgRNA for spCas9 were designed using webtools – CRISPR-P 2.0 design tool (http://crispr.hzau.edu.cn/CRISPR2/) (67) and Benchling (https://www.benchling.com).…”

Induced ligno-suberin vascular coating and tyramine-derived hydroxycinnamic acid amides restrict Ralstonia solanacearum colonization in resistant tomato roots

“…The interaction between the soil-borne bacterial wilt pathogen Ralstonia solanacearum and tomato offers a paradigmatic scenario to study inducible physico-chemical barriers, because of its agro-economic impact, and the well-developed genetic and molecular tools available in both organisms. R. solanacearum enters the root system through wounds or at the points of emergence of lateral roots, where the epidermal barrier may be compromised, and both the endodermis and Casparian strip are either not fully differentiated or reoriented and endodermal suberin overlying the primordium is being degraded (Vasse et al ., 1995; Álvarez et al ., 2010; Ursache et al ., 2021) After entering the root, the bacterium moves centripetally towards the vasculature and once it reaches the xylem, it multiplies and spreads vertically within the vessels and horizontally to other vessels and the surrounding tissues (Digonnet et al ., 2012).…”