Transcription Factor ERF194 Modulates the Stress-Related Physiology to Enhance Drought Tolerance of Poplar

Woody plant cell walls: Fundamentals and utilization

Cell walls in plants, particularly forest trees, are the major carbon sink of the terrestrial ecosystem. Chemical and biosynthetic features of plant cell walls were revealed early on, focusing mostly on herbaceous model species. Recent developments in genomics, transcriptomics, epigenomics, transgenesis, and associated analytical techniques are enabling novel insights into formation of woody cell walls. Here, we review multilevel regulation of cell wall biosynthesis in forest tree species. We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees. We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.

PagMYB205 Negatively Affects Poplar Salt Tolerance through Reactive Oxygen Species Scavenging and Root Vitality Modulation

Salt stress is one of the major abiotic stresses that limits plant growth and development. The MYB transcription factor family plays essential roles in plant growth and development, as well as stress tolerance processes. In this study, the cDNA of the 84K poplar (Populus abla × Populus glandulosa) was used as a template to clone the full length of the PagMYB205 gene fragment, and transgenic poplar lines with PagMYB205 overexpression (OX) or inhibited expression (RNAi, RNA interference) were cultivated. The role of PagMYB205 in poplar growth and development and salt tolerance was detected using morphological and physiological methods. The full-length CDS sequence of PagMYB205 was 906 bp, encoding 301 amino acids, and the upstream promoter sequence contained abiotic stress-related cis-acting elements. The results of subcellular localization and transactivation assays showed that the protein had no self-activating activity and was localized in the nucleus. Under salt stress, the rooting rate and root vitality of RNAi were higher than OX and wild type (WT). However, the malondialdehyde (MDA) content of the RNAi lines was significantly lower than that of the wild-type (WT) and OX lines, but the reactive oxygen species (ROS) scavenging ability, such as the peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzyme activities, was dramatically more powerful. Most significantly of all, the RNAi3 line with the lowest expression level of PagMYB205 had the lowest MDA content, the best enzyme activity and root vitality, and the best salt stress tolerance compared to the other lines. The above results suggest that the transcription factor PagMYB205 could negatively regulate salt stress tolerance by regulating antioxidant enzyme activity and root vitality.

PagMYB151 facilitates proline accumulation to enhance salt tolerance of poplar

Poplar is one of the main urban and rural greening and shade tree species in the northern hemisphere, but its growth and development is always restricted by salt stress. R2R3-MYB transcription factor family is commonly involved in many biological processes during plant growth and stress endurance. In this study, PagMYB151 (Potri.014G035100) one of R2R3-MYB members related to salt stress and expressed in both nucleus and cell membrane was cloned from Populus alba × P. glandulosa to perfect the salt tolerance mechanism. Morphological and physiological indexes regulated by PagMYB151 were detected using the PagMYB151 overexpression (OX) and RNA interference (RNAi) transgenic poplar lines. Under salt stress conditions, compared with RNAi and the non-transgenic wild-type (WT) plants, the plant height, both aboveground and underground part fresh weight of OX was significantly increased. In addition, OX has a longer and finer root structure and a larger root surface area. The root activity of OX was also enhanced, which was significantly different from RNAi but not from WT under salt treatment. Under normal conditions, the stomatal aperture of OX was larger than WT, whereas this phenotype was not obvious after salt stress treatment. In terms of physiological indices, OX enhanced the accumulation of proline but reduced the toxicity of malondialdehyde to plants under salt stress. Combing with the transcriptome sequencing data, 6 transcription factors induced by salt stress and co-expressed with PagMYB151 were identified that may cooperate with PagMYB151 to function in salt stress responding process. This study provides a basis for further exploring the molecular mechanism of poplar PagMYB151 transcription factor under abiotic stress.