@article{morse_whetten_dubos_campbell_2009, title={Post-translational modification of an R2R3-MYB transcription factor by a MAP Kinase during xylem development}, volume={183}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2009.02900.x}, abstractNote={Despite the pivotal role played by R2R3-MYB family members in the regulation of plant gene expression, little is known about post-translational regulation of these proteins. In animals, the MYB family member, c-MYB, is post-translationally modified by a mitogen-activated protein kinase (MAPK), p42(mapk). In order to test the hypothesis that R2R3-MYB proteins may be regulated by MAPK activity, interplay between a R2R3-MYB family member expressed in differentiating pine xylem (Pinus taeda MYB4, PtMYB4) and MAPK proteins expressed in the same tissue was examined. One of the MAPK proteins expressed in pine xylem, PtMAPK6, phosphorylated PtMYB4. Recombinant PtMAPK6 phosphorylated PtMYB4 on serine-236, located in the C-terminal activation domain of this transcription factor in a context that is found in other plant MYB proteins. Modification of the PtMAPK6 target serine in PtMYB4 did not appear to alter DNA binding in vitro but did alter the ability of PtMYB4 to promote transcriptional activation in yeast. PtMAPK6 activity was detected in developing xylem cells that had ceased cell division and formed secondary walls. Together, the data support a role for PtMAPK6 during early xylem development and suggest a function for this kinase in regulating gene expression through phosphorylation of PtMYB4.}, number={4}, journal={NEW PHYTOLOGIST}, author={Morse, Alison M. and Whetten, Ross W. and Dubos, Christian and Campbell, Malcolm M.}, year={2009}, pages={1001–1013} }
 @article{campbell_sederoff_1996, title={Variation in lignin content and composition - Mechanism of control and implications for the genetic improvement of plants}, volume={110}, ISSN={["1532-2548"]}, DOI={10.1104/pp.110.1.3}, abstractNote={Lignin, a complex phenolic polymer, is important for mechanical support, water transport, and defense in vaseular plants. Compressive strength and hydrophobicity of xylem cell walls are imparted by the lignin polymer, which is deposited during the terminal differentiation of tracheids and other cell types. The resistance of xylem to compressive stresses imposed by water transport and by the mass of the plants is important to growth and development. In addition, the insolubility and complexity of the lignin polymer makes it resistant to degradation by most microorganisms. Therefore, lignin serves an important function in plant defense. Variation in lignin content, composition, and location is likely to affect these essential processes. The constraints on the amount, composition, and localization of lignin for normal xylem function and plant defense are not known. Lignin composition, quantity, and distribution also affect the agroindustrial uses of plant material. Digestibility and dietary conversion of herbaceous crops are affected by differences in lignin content and composition (Akin et al., 1986, 1991). Lignin is an undesirable component in the conversion of wood into pulp and paper; remova1 of lignin is a major step in the paper making process. Furthermore, the resistance of lignin to microbial degradation enhances its persistence in soils. Lignin is, therefore, a significant component in the global carbon cycle. The mechanisms of control of lignin composition and quantity have wide implications regarding the adaptation and evolution of land plants and provide a basis for improved genetic manipulation of lignin for agroindustrial end uses. In this Update, we will focus on the levels of control of lignin variation, including (a) metabolic control, (b) regulation of individual enzymes in the biosynthetic pathway, and (c) regulation of gene expression. These levels of regulation affect variation in lignin content, quality, and distribution. Finally, the implications of these regulatory mechanisms for the genetic improvement of lignin for}, number={1}, journal={PLANT PHYSIOLOGY}, author={Campbell, MM and Sederoff, RR}, year={1996}, month={Jan}, pages={3–13} }