To cope with environmental fluctuations and to prevent invasion by pathogens, plant metabolism must be flexible and dynamic. Active oxygen species, whose formation is accelerated under stress conditions, must be rapidly processed if oxidative damage is to be averted. The lifetime of active oxygen species within the cellular environment is determined by the antioxidative system, which provides crucial protection against oxidative damage. The antioxidative system comprises numerous enzymes and compounds of low molecular weight. While research into the former has benefited greatly from advances in molecular technology, the pathways by which the latter are synthesized have received comparatively little attention. The present review emphasizes the roles of ascorbate and glutathione in plant metabolism and stress tolerance. We provide a detailed account of current knowledge of the biosynthesis, compartmentation, and transport of these two important antioxidants, with emphasis on the unique insights and advances gained by molecular exploration.

ASCORBATE AND GLUTATHIONE: Keeping Active Oxygen Under Control

https://www.cell.com/trends/plant-science/pdf/S1360-1385(02)02251-3.pdf

GATEWAY vectors for Agrobacterium-mediated plant transformation.

Jasmonates: biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany

Studies of the molecular genetics, mechanisms of activation and functional connections between general phenylpropanoid metabolism and certain branch pathways in parsley, bean, potato plants and cell cultures

Physiology and Molecular Biology of Phenylpropanoid Metabolism

Plants sense potential microbial invaders by using pattern-recognition receptors to recognize pathogen-associated molecular patterns (PAMPs). In Arabidopsis thaliana, the leucine-rich repeat receptor kinases flagellin-sensitive 2 (FLS2) (ref. 2) and elongation factor Tu receptor (EFR) (ref. 3) act as pattern-recognition receptors for the bacterial PAMPs flagellin and elongation factor Tu (EF-Tu) (ref. 5) and contribute to resistance against bacterial pathogens. Little is known about the molecular mechanisms that link receptor activation to intracellular signal transduction. Here we show that BAK1 (BRI1-associated receptor kinase 1), a leucine-rich repeat receptor-like kinase that has been reported to regulate the brassinosteroid receptor BRI1 (refs 6,7), is involved in signalling by FLS2 and EFR. Plants carrying bak1 mutations show normal flagellin binding but abnormal early and late flagellin-triggered responses, indicating that BAK1 acts as a positive regulator in signalling. The bak1-mutant plants also show a reduction in early, but not late, EF-Tu-triggered responses. The decrease in responses to PAMPs is not due to reduced sensitivity to brassinosteroids. We provide evidence that FLS2 and BAK1 form a complex in vivo, in a specific ligand-dependent manner, within the first minutes of stimulation with flagellin. Thus, BAK1 is not only associated with developmental regulation through the plant hormone receptor BRI1 (refs 6,7), but also has a functional role in PRR-dependent signalling, which initiates innate immunity.

/pdf/a-flagellin-induced-complex-of-the-receptor-fls2-and-bak1-357o3yyeyl.pdf

A flagellin-induced complex of the receptor FLS2 and BAK1 initiates plant defence

*† ‡ § Summary Brassinosteroids (BRs) regulate multiple aspects of plant growth and development and require an active BRASSINOSTEROID-INSENSITIVE 1 (BRI1) receptor serine/threonine kinase for hormone perception and signal transduction. In mammals, the transforming growth factor-beta (TGF-b) family of polypeptides modulate numerous aspects of development and are perceived at the cell surface by a complex of type I and type II TGF-b receptor serine/threonine kinases. TGF-b receptor interacting protein (TRIP-1) is a cytoplasmic substrate of the TGF-b type II receptor kinase and plays a role in TGF-b signaling. TRIP-1 is a WD domain protein that also functions as an essential subunit of the eIF3 eukaryotic translation initiation factor in animals, yeast and plants. We previously cloned putative TRIP-1 homologs from bean and Arabidopsis and found that transgenic Arabidopsis plants expressing antisense TRIP-1 RNA exhibited a broad range of developmental defects including some morphological characteristics that resemble the phenotype of BR-deficient and insensitive mutants. We now show that the BRI1 kinase domain phosphorylates Arabidopsis TRIP-1 on three specific sites in vitro (Thr-14, Thr-89 and either Thr-197 or Ser-198). Co-immunoprecipitation experiments using antibodies against TRIP-1, BRI1 and various fusion proteins strongly suggest that TRIP-1 and BRI1 also interact directly in vivo. These findings support a role for TRIP-1 in the molecular mechanisms of BR-regulated plant growth and development, possibly as a cytoplasmic substrate of the BRI1 receptor kinase.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2005.02448.x

Interaction of Arabidopsis BRASSINOSTEROID‐INSENSITIVE 1 receptor kinase with a homolog of mammalian TGF‐β receptor interacting protein

Plant development: a role for sterols in embryogenesis.

https://www.cell.com/trends/plant-science/pdf/S1360-1385(01)02102-1.pdf

Integration of light and brassinosteroid signals in etiolated seedling growth

Direct Modulation of Heterotrimeric G Protein-coupled Signaling by a Receptor Kinase Complex.

The transition from vegetative to reproductive growth in plants is a major developmental switch regulated by a set of complex, integrated signal transduction pathways that respond to both environmental cues and endogenous signals to alter the expression of genes associated with the initiation and development of floral organs (1). Understanding the molecular mechanisms of flowering has both intrinsic scientific interest and immense practical agricultural applications. In many plants, the timing of flowering is regulated by light quality and quantity, temperature, and the action of gibberellins (GAs), a class of plant hormones with pleiotropic effects on both vegetative and reproductive development (2). Another class of plant hormones, the brassinosteroids (BRs), also regulates multiple aspects of plant development (3), and recent evidence suggests that BRs stimulate flowering by reducing transcript levels of a potent floral repressor (4). As with many other developmental processes in plants, our understanding of molecular events underlying floral initiation has been greatly advanced by studying mutants in the model plant Arabidopsis thaliana. The molecular genetic analysis of Arabidopsis mutants exhibiting early or delayed flowering has uncovered numerous critical components of signal transduction pathways regulating response to photoperiod, hormones, and cold treatment. Similarly, analysis of mutants with defective BR perception or response has provided extensive details on the molecular components required for BR signaling (5, 6). In this issue of PNAS, Yu et al. (7) provide a connection between BR signal transduction and pathways controlling floral initiation by demonstrating that a critical …

https://www.pnas.org/content/pnas/105/21/7345.full.pdf

Steven D. Clouse

Papers

Interaction of Arabidopsis BRASSINOSTEROID‐INSENSITIVE 1 receptor kinase with a homolog of mammalian TGF‐β receptor interacting protein

Plant development: a role for sterols in embryogenesis.

Integration of light and brassinosteroid signals in etiolated seedling growth

Direct Modulation of Heterotrimeric G Protein-coupled Signaling by a Receptor Kinase Complex.

The molecular intersection of brassinosteroid-regulated growth and flowering in Arabidopsis