Role of MYB Transcription Factors During Phellem Differentiation

Abstract

The periderm is a crucial protective barrier that plays a vital role in secondary growth. It is a multi-layered tissue composed anatomically of three layers: the phellem or cork, the phellogen or cork cambium, and the phelloderm. The phellogen, a meristematic layer, undergoes bifacial divisions, generating the phellem outward and the phelloderm inward. The phellem comprises specialized cells that accumulate substantial amounts of suberin and lignin, providing it with an exceptional protective capacity. This accumulation holds significant potential for plant breeding and biotechnological applications. However, there is still very little knowledge regarding the regulatory mechanisms governing phellem differentiation and the specific accumulation of apoplastic barriers. Arabidopsis root has emerged as a significant model for studying the periderm, facilitating the understanding of this process. In our research, we explore the role of the MYB68 clade transcription factor in regulating phellem differentiation in the Arabidopsis periderm. Our findings reveal that overexpression of MYB68 in the periderm triggers phellem differentiation. This differentiation process involves an increase in suberin deposition, facilitated by the upregulation of genes related to suberin polymerization and biosynthesis. Additionally, our study demonstrates that aside from regulating apoplastic barriers, MYB68 deactivates the meristematic activity of the phellogen. Notably, in certain loss-of-function mutants of this clade, we observe a delay in phellem differentiation. As a complementary aspect of our research, we seek to gain a better understanding of the significance of apoplastic barrier establishment in the periderm. Firstly, we explore whether the periderm can respond to issues affecting the apoplastic barrier. In our research, we suggest that the Schengen pathway plays two pivotal roles: first, in the specific polymerization of the apoplastic barrier in the phellem, and second, in serving as a part of a surveillance system that monitors barrier integrity. Secondly, we demonstrate the importance of the aromatic monomers produced in the phenylproanoid pathway for the proper establishment of apoplastic barriers in the phellem. This work contributes to our understanding of the molecular mechanisms underlying periderm development, particularly in relation to phellem differentiation and the establishment of apoplastic barriers. We aim to provide useful tools and concepts that will aid in the design of new biotechnological tools to improve agricultural activities and offer sustainable alternatives for production.

Die Dissertation ist gesperrt bis zum 13. Dezember 2025 !