Subgroup 4 R2R3-MYBs in conifer trees: gene family expansion and contribution to the isoprenoid- and flavonoid-oriented responses

Transcription factors play a fundamental role in plants by orchestrating temporal and spatial gene expression in response to environmental stimuli. Several R2R3-MYB genes of the Arabidopsis subgroup 4 (Sg4) share a C-terminal EAR motif signature recently linked to stress response in angiosperm plants. It is reported here that nearly all Sg4 MYB genes in the conifer trees Picea glauca (white spruce) and Pinus taeda (loblolly pine) form a monophyletic clade (Sg4C) that expanded following the split of gymnosperm and angiosperm lineages. Deeper sequencing in P. glauca identified 10 distinct Sg4C sequences, indicating over-represention of Sg4 sequences compared with angiosperms such as Arabidopsis, Oryza, Vitis, and Populus. The Sg4C MYBs share the EAR motif core. Many of them had stress-responsive transcript profiles after wounding, jasmonic acid (JA) treatment, or exposure to cold in P. glauca and P. taeda, with MYB14 transcripts accumulating most strongly and rapidly. Functional characterization was initiated by expressing the P. taeda MYB14 (PtMYB14) gene in transgenic P. glauca plantlets with a tissue-preferential promoter (cinnamyl alcohol dehydrogenase) and a ubiquitous gene promoter (ubiquitin). Histological, metabolite, and transcript (microarray and targeted quantitiative real-time PCR) analyses of PtMYB14 transgenics, coupled with mechanical wounding and JA application experiments on wild-type plantlets, allowed identification of PtMYB14 as a putative regulator of an isoprenoid-oriented response that leads to the accumulation of sesquiterpene in conifers. Data further suggested that PtMYB14 may contribute to a broad defence response implicating flavonoids. This study also addresses the potential involvement of closely related Sg4C sequences in stress responses and plant evolution

Targeted Grazing: Applying the Research to the Land

The discipline of range science is in part based on the observation that vegetation on rangelands changes in response to livestock grazing. For much of the history of range science, livestock grazing was considered to affect range plants and ecological condition negatively. Thus range plants were classified as increasers, decreasers, or invaders as a function of their response to grazing. The concept that grazing can be used to restore degraded rangelands is relatively new. It requires a paradigm shift for most people from grazing animals reaping the benefits of the land to the land reaping the benefits of the grazing animals. Using livestock to accomplish vegetation management goals is referred to as targeted grazing. Targeted grazing is defined as the application of a particular kind of grazing animal at a specified season, duration, and intensity to accomplish specific vegetation management goals. It is the last half of this definition that differentiates targeted grazing from traditional grazing. The focus is on the vegetation and the subsequent outcomes and changes in composition or structure, rather than the performance of the grazing animal. Where the potential for targeted grazing to create positive change on the landscape has been clearly demonstrated through research and the experiences of practitioners, it still struggles to gain recognition as a viable vegetation management option. The recently published handbook Targeted Grazing: A Natural Approach to Vegetation Management and Landscape Enhancement was organized and written largely by range scientists to provide the scientific basis for targeted grazing. However, it did not provide much information on the practical and daily management decisions required by contract graziers and land managers. While the scientific basis for targeted grazing provides the foundation for understanding and improving this technology, as with all grazing management it is the daily operations and decisions that determine its success. The diversity of situations to which this tool can be applied necessitates the exchange of real-life experiences to promote learning among practitioners and to inform land managers of the successful programs and potential pitfalls to avoid....The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202