AtMYB41 activates ectopic suberin synthesis and assembly in multiple plant species and cell types.
Bottom Line: Suberin is a lipid and phenolic cell wall heteropolymer found in the roots and other organs of all vascular plants.Overexpression of AtMYB41 also resulted in elevated amounts of monolignols in leaves and an increase in the accumulation of phenylpropanoid and lignin biosynthetic gene transcripts.These results provide insight into the molecular-genetic mechanisms of the biosynthesis and deposition of a ubiquitous cell wall-associated plant structure and will serve as a basis for discovering the transcriptional network behind one of the most abundant lipid-based polymers in nature.
Affiliation: Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.Show MeSH
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Mentions: The chemical and ultrastructural phenotypes observed in AtMYB41-overexpressing Arabidopsis plants were also observed when AtMYB41 was transiently overexpressed in Nicotiana benthamiana leaves under the control of the 35S promoter (Figure3). In total, leaves possessed 22 times more suberin-type monomers than cutin-type monomers after 6 days of AtMYB41 expression (Figure3). This included a 49-fold increase in ferulic acid, 17-fold increases in 16:0 and 18:1 ω-OH FAs, >85-fold increases in 20:0–24:0 DCAs and ω-OH FAs, and 15- to 55-fold increases in 20:0–24:0 fatty acids (Figure3). Transmission electron microscopy (TEM) images of leaf cross sections revealed the presence of distinct lamellae abutting the internal surfaces of the primary cell walls of epidermal cells (Figure3) and mesophyll cells (Figure S8). These lamellar structures bore a striking resemblance to the lamellae normally found in the cell walls of suberized peridermis and endodermis cells from mature and young roots, respectively (Figure S5). Transient expression of other candidate R2-R3 MYB transcription factors identified from transcriptional co-expression analysis (Table S1), AtMYB45 (At3g48920) and AtMYB67 (At3g12720), in leaves of N. benthamiana did not result in the accumulation of suberin-type monomers (Figure S9). Similarly, the infiltration process did not appear to induce the accumulation of suberin-type monomers as a response to the wounding that could potentially occur during infiltration (Figure S9). Collectively, these results show that AtMYB41 overexpression is sufficient to induce a number of activities required to form suberin-like lamellae with a full complement of aliphatic suberin-type components. The lack of suberin-type monomer production via expression of other candidate MYBs indicates that AtMYB41 specifically induces aliphatic suberin production and that the production of suberin aliphatics in N. benthamiana leaves is not a general consequence of overexpressing Arabidopsis MYB transcription factors. Similarly, the observed induction of suberin-type monomers by transient overexpression of AtMYB41 is not a general consequence of wounding by the infiltration process.
Affiliation: Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.