The cinnamyl alcohol dehydrogenase gene family in Populus: phylogeny, organization, and expression

<p>Abstract</p> <p>Background</p> <p>Lignin is a phenolic heteropolymer in secondary cell walls that plays a major role in the development of plants and their defense against pathogens. The biosynthesis of monolignols, which represent the main component of lignin involves many enzymes. The cinnamyl alcohol dehydrogenase (CAD) is a key enzyme in lignin biosynthesis as it catalyzes the final step in the synthesis of monolignols. The CAD gene family has been studied in <it>Arabidopsis thaliana, Oryza sativa </it>and partially in <it>Populus</it>. This is the first comprehensive study on the CAD gene family in woody plants including genome organization, gene structure, phylogeny across land plant lineages, and expression profiling in <it>Populus</it>.</p> <p>Results</p> <p>The phylogenetic analyses showed that CAD genes fall into three main classes (clades), one of which is represented by CAD sequences from gymnosperms and angiosperms. The other two clades are represented by sequences only from angiosperms. All <it>Populus </it>CAD genes, except <it>PoptrCAD 4 </it>are distributed in Class II and Class III. CAD genes associated with xylem development (<it>PoptrCAD 4 and PoptrCAD 10</it>) belong to Class I and Class II. Most of the CAD genes are physically distributed on duplicated blocks and are still in conserved locations on the homeologous duplicated blocks. Promoter analysis of CAD genes revealed several motifs involved in gene expression modulation under various biological and physiological processes. The CAD genes showed different expression patterns in poplar with only two genes preferentially expressed in xylem tissues during lignin biosynthesis.</p> <p>Conclusion</p> <p>The phylogeny of CAD genes suggests that the radiation of this gene family may have occurred in the early ancestry of angiosperms. Gene distribution on the chromosomes of <it>Populus </it>showed that both large scale and tandem duplications contributed significantly to the CAD gene family expansion. The duplication of several CAD genes seems to be associated with a genome duplication event that happened in the ancestor of <it>Salicaceae</it>. Phylogenetic analyses associated with expression profiling and results from previous studies suggest that CAD genes involved in wood development belong to Class I and Class II. The other CAD genes from Class II and Class III may function in plant tissues under biotic stresses. The conservation of most duplicated CAD genes, the differential distribution of motifs in their promoter regions, and the divergence of their expression profiles in various tissues of <it>Populus </it>plants indicate that genes in the CAD family have evolved tissue-specialized expression profiles and may have divergent functions.</p

Physio-Genetic Dissection of Dark-Induced Leaf Senescence and Timing Its Reversal in Barley.

Barley crop model was analyzed for early and late events during the dark-induced leaf senescence (DILS) as well as for deciphering critical time limit for reversal of the senescence process. Chlorophyll fluorescence vitality index Rfd was determined as the earliest parameter that correlated well with the cessation of photosynthesis prior to microautophagy symptoms, initiation of DNA degradation, and severalfold increase in the endonuclease BNUC1. DILS was found characterized by up-regulation of processes that enable recycling of degraded macromolecules and metabolites, including increased NH4+ remobilization, gluconeogenesis, glycolysis, and partial up-regulation of glyoxylate and tricarboxylate acid cycles. The most evident differences in gene medleys between DILS and developmental senescence included hormone-activated signaling pathways, lipid catabolic processes, carbohydrate metabolic processes, low-affinity ammonia remobilization, and RNA methylation. The mega-autophagy symptoms were apparent much later, specifically on day 10 of DILS, when disruption of organelles—nucleus and mitochondria —became evident. Also, during this latter-stage programmed cell death processes, namely, shrinking of the protoplast, tonoplast interruption, and vacuole breakdown, chromatin condensation, more DNA fragmentation, and disintegration of the cell membrane were prominent. Reversal of DILS by re-exposure of the plants from dark to light was possible until but not later than day 7 of dark exposure and was accompanied by regained photosynthesis, increase in chlorophyll, and reversal of Rfd, despite activation of macro-autophagy-related genes

Abscisic Acid and Jasmonate Metabolisms Are Jointly Regulated During Senescence in Roots and Leaves of Populus trichocarpa

Plant senescence is a highly regulated process that allows nutrients to be mobilized from dying tissues to other organs. Despite that senescence has been extensively studied in leaves, the senescence of ephemeral organs located underground is still poorly understood, especially in the context of phytohormone engagement. The present study focused on filling this knowledge gap by examining the roles of abscisic acid (ABA) and jasmonate in the regulation of senescence of fine, absorptive roots and leaves of Populus trichocarpa. Immunohistochemical (IHC), chromatographic, and molecular methods were utilized to achieve this objective. A transcriptomic analysis identified significant changes in gene expression that were associated with the metabolism and signal transduction of phytohormones, especially ABA and jasmonate. The increased level of these phytohormones during senescence was detected in both organs and was confirmed by IHC. Based on the obtained data, we suggest that phytohormonal regulation of senescence in roots and leaves is organ-specific. We have shown that the regulation of ABA and JA metabolism is tightly regulated during senescence processes in both leaves and roots. The results were discussed with respect to the role of ABA in cold tolerance and the role of JA in resistance to pathogens

Dehydration Sensitivity at the Early Seedling Establishment Stages of the European Beech (Fagus sylvatica L.)

Shortage of water is a limiting factor for the growth and development of plants, particularly at early developmental stages. We focused on the European beech (Fagus sylvatica L.), which produces seeds and further seedlings in large intervals of up to ten years. To explore the beech seedling establishment process, six stages referring to embryo expansion were studied to determine sensitivity to dehydration. The characterization of the response of elongating embryonic axes and cotyledons included a viability test before and after dehydration and measurement of the amounts of electrolyte leakage, concentration, and arrangement of storage materials, changes in chaperone proteins related to water deficit, and accumulation of hydrogen peroxide and superoxide anion radicals. Elongating embryonic axes and cotyledons differed in water content, dehydration rates, membrane permeability before and after dehydration, protein, and lipid decomposition pattern, and amount of 44-kDa dehydrin and 22-kDa small heat shock protein (sHSP). Protruding embryonic axes were more sensitive to dehydration than cotyledons, although dehydration caused transient reinduction of three dehydrin-like proteins and sHSP synthesis, which accompany desiccation tolerance. Extended deterioration, including overproduction of hydrogen peroxide and depletion of superoxide anion radicals, was reported in dehydrated embryonic axes longer than 10 mm characterized by highly elevated cellular leakage. The apical part elongating embryonic axes consisting of the radicles was the most sensitive part of the seed to dehydration, and the root apical meristem area was the first to become inviable. The effects of severe dehydration involving ROS imbalance and reduced viability in beech seedlings with embryonic axes longer than 10 mm might help to explain the difficulties in beech seedling establishment observed in drought-affected environments. The conversion of environmental drought into climate-originated oxidative stress affecting beech seedling performance is discussed in this report

Allies or Enemies: The Role of Reactive Oxygen Species in Developmental Processes of Black Cottonwood (Populus trichocarpa)

In contrast to aboveground organs (stems and leaves), developmental events and their regulation in underground organs, such as pioneer and fine roots, are quite poorly understood. The objective of the current study was to achieve a better understanding of the physiological and molecular role of reactive oxygen species (ROS) and ROS-related enzymes in the process of stem and pioneer root development in black cottonwood (Populus trichocarpa), as well as in the senescence of leaves and fine roots. Results of a transcriptomic analysis revealed that primary/secondary growth and senescence are accompanied by substantial changes in the expression of genes related to oxidative stress metabolism. We observed that some mechanisms common for above- and under-ground organs, e.g., the expression of superoxide dismutase (SOD) genes and SOD activity, declined during stems&rsquo; and pioneer roots&rsquo; development. Moreover, the localization of hydrogen peroxide (H2O2) and superoxide (O2&bull;&ndash;) in the primary and secondary xylem of stems and pioneer roots confirms their involvement in xylem cell wall lignification and the induction of programmed cell death (PCD). H2O2 and O2&bull;&ndash; in senescing fine roots were present in the same locations as demonstrated previously for ATG8 (AuTophaGy-related) proteins, implying their participation in cell degradation during senescence, while O2&bull;&ndash; in older leaves was also localized similarly to ATG8 in chloroplasts, suggesting their role in chlorophagy. ROS and ROS-related enzymes play an integral role in the lignification of xylem cell walls in Populus trichocarpa, as well as the induction of PCD during xylogenesis and senescence

How to explore what is hidden? A review of techniques for vascular tissue expression profile analysis

Abstract The evolution of plants to efficiently transport water and assimilates over long distances is a major evolutionary success that facilitated their growth and colonization of land. Vascular tissues, namely xylem and phloem, are characterized by high specialization, cell heterogeneity, and diverse cell components. During differentiation and maturation, these tissues undergo an irreversible sequence of events, leading to complete protoplast degradation in xylem or partial degradation in phloem, enabling their undisturbed conductive function. Due to the unique nature of vascular tissue, and the poorly understood processes involved in xylem and phloem development, studying the molecular basis of tissue differentiation is challenging. In this review, we focus on methods crucial for gene expression research in conductive tissues, emphasizing the importance of initial anatomical analysis and appropriate material selection. We trace the expansion of molecular techniques in vascular gene expression studies and discuss the application of single-cell RNA sequencing, a high-throughput technique that has revolutionized transcriptomic analysis. We explore how single-cell RNA sequencing will enhance our knowledge of gene expression in conductive tissues

Integration of MsrB1 and MsrB2 in the Redox Network during the Development of Orthodox and Recalcitrant Acer Seeds

International audienceTwo related tree species, Norway maple (Acer platanoides L.) and sycamore (Acer pseudoplatanus L.), produce desiccation-tolerant (orthodox) and desiccation-sensitive (recalcitrant) seeds, respectively. We compared the seeds of these two species to characterize the developmentally driven changes in the levels of peptide-bound methionine sulfoxide (MetO) and the abundance of methionine sulfoxide reductases (Msrs) B1 and B2, with respect to the cellular redox environment. Protein oxidation at the Met level was dynamic only in Norway maple seeds, and the reduced MsrB2 form was detected only in this species. Cell redox status, characterized by the levels of reduced and oxidized ascorbate, glutathione, and nicotinamide adenine dinucleotide (NAD)/phosphate (NADP), was clearly more reduced in the Norway maple seeds than in the sycamore seeds. Clear correlations between MetO levels, changes in water content and redox status were reported in orthodox Acer seeds. The abundance of Msrs was correlated in both species with redox determinants, mainly ascorbate and glutathione. Our data suggest that MsrB2 is associated with the acquisition of desiccation tolerance and that ascorbate might be involved in the redox pathway enabling the regeneration of Msr via intermediates that are not known yet