Evaluation of Translational Control Mechanisms in Response to Oxygen Deprivation in Maize

Abstract

-Numerous changes in gene expression occur in response to flooding (oxygen deprivation, i.e., anoxia and hypoxia) in seedling roots of maize ( Zea mays L.) and other plants. Increased de novo transcription of anaerobic polypeptide (ANP) genes is responsible, in part for increased production of glycolytic and fermentative enzymes, such as alcohol dehydrogenase-1. There is increasing evidence that regulation of mRNA translation plays an important role in the expression of ANP genes during oxygen deprivation. By quantitative analysis of ribosomal complexes, we demonstrated a dramatic decrease in polysomes and an increase in monosomes in maize seedling roots deprived of oxygen, indicative of regulation of translational initiation. We report that oxygen deprivation causes dynamic changes in the phosphorylation status of the eukaryotic initiation factors (eIF) eIF4E, eIF4A, and eIF4B. By affinity purification of initiation complexes with 7m GTP and poly(A) resins, we demonstrate that a reduction in pH, which occurs in the cytosol in response to this stress, affects the assembly of mRNA 5'-cap and 3'-tail-binding complexes. We also describe oxygen deprivation-induced changes in phosphorylation of ribosomal protein S6, ribosomal 12-kD P-proteins and eukaryotic elongation factor-2 (eEF2). A model is presented that considers the implication of modifications in translational machinery in the interactions between the 5'-cap and 3'-tail of the mRNA that facilitate initiation and eEF2 GTPase activity which promotes elongation.

Plant Anaerobic Stress as a Novel Trend in Ecological Physiology, Biochemistry, and Molecular Biology: 1. Establishment of a New Scientific Discipline

“…Later, our data were supported by the teams of Armstrong [74] and Ap Rees [75], which had far-reaching consequences. Firstly, one of the main statements of Crawford's metabolic theory [32][33][34], according to which the roots of plants inhabiting flooded anaerobic soils manifest a high resistance to anoxia due to metabolism rearrangement, was invalidated. Secondly, the results of our investigations permitted us to conclude that a capability of flood-tolerant plants of living on anaerobic soils is explained not by biochemical properties of their roots but by the avoidance of anaerobiosis due to oxygen transport from aboveground aerated organs to roots located in oxygen-free medium.…”

“…Analyzing the development of our knowledge of hypoxic and anoxic stresses during the last three decades, the author chose Crawford's metabolic theory [32][33][34] as an initial point on the following reasons. Firstly, this was the first theory, which seemingly gave a definite answer to both critical issues of plant life under anaerobiosis, the mechanisms of their damage and adaptation.…”

“…It is worth mentioning that anoxia-intolerant Echinochloa species did not produce anaerobic proteins [150]. The control of anaerobic protein synthesis at the transcriptional, translational, and posttranslational levels is currently studied actively [26][27][28][29][30][31][32][33]. Expression of genes responsible for the synthesis of anaerobic proteins, predominantly the enzymes of glycolysis and ethanolic fermentation, was demonstrated under anaerobiosis conditions not only in the laboratory experiments but also in natural environment during studying of Acorus calamus rhizomes, which could be long time under oxygen deficiency during winter [151].…”

“…The significance of this problem from point of view of basic research, applied agronomy, and forestry, and its economical and ecological importance became commonly recognized. The interest to it increased not only among plant ecologists, physiologists, and biochemists [8][9][10] but also among molecular biologists and molecular geneticists [26][27][28][29][30][31][32][33]. Scientists from various countries attempted not only to elucidate the mechanisms of plant damage and adaptation under conditions of oxygen deficiency but also to create plant organisms more flood-tolerant to anaerobic stress.…”

Identification of Water Deficit Stress Upregulated Genes in Sugarcane

“…Transcriptional and translational regulation plays important role in stress alleviation (Szick-Miranda et al 2003). The regulatory proteins found in our ESTs include AP2 domain containing transcription factor (ES697549), MYB (FF682668), WRKY (FE840572), LIM (ES697505), and snRNP splicing factor (FE840489).…”