Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al. Adaptation versus Acclimation Adaptation - evolutionary changes that
enable an organism to exploit a certain niche. These include modification of existing genes, as well as gain/loss of genes. e.g., thermo-stable enzymes in organisms that tolerate high temperature Acclimation inducible responses that enable an organism to tolerate an unfavorable or lethal change in their environment. e.g., heat shock response Types of Stress
Biotic 1.pathogens 2.herbivores Plants respond to stresses as individual cells and as whole organisms stress induced signals can be transmitted throughout the plant, making other parts more ready to withstand the stress.. Fig. 22.3, Buchanan et al. Most organisms are adapted to environmental temperature:
1. 2. 3. 4. Psychrophiles (< 20 C) Mesophiles (~ 20-35 C) Thermophiles ( ~35-70 ) Hyperthermophiles (70-110 C) Groups 1,3 & 4 are a.k.a. Extremophiles
But can also acclimate to extreme shifts, if they are not permanent, and not too extreme. Two well studied acclimation responses are: 1. the Heat Shock response 2. Cold acclimation Heat Stress (or Heat Shock) Response Induced by temperatures ~10-15oC above normal Ubiquitous (conserved), rapid & transient Dramatic change in pattern of protein synthesis induction (increase) of HSPs
most HSPs are chaperones (chaperonins) that promote protein re-folding & stability HSP induction mediated by a bZIP factor, HSF Fig. 22.43, Buchanan et al. Thermotolerant growth of soybean seedlings following a heat shock. 28oC Soybean seedlings.
40oC 45oC 45oC Fig. 22.42, Buchanan et al. Heat stress effects on protein synthesis in soybean seedlings (J. Key). Joe Key Cold Acclimation (CA) involves:
Increased accumulation of small solutes retain water & stabilize proteins e.g., proline, glycine betaine, trehalose Altered membrane lipids, to lower gelling temp. Changes in gene expression [e.g., antifreeze proteins, proteases, RNA-binding proteins (?)] Many cold-regulated promoters have DRE/C-elements Activated by CBF1 transcription factor Role of ABA (stress hormone)
ABA Abscisic acid, phytohormone induced by wilting, closes stomata by acting on guard cells Positive correlation between CA and [ABA] Treat plants with ABA, and they will be somewhat cold hardened However, ABA does not induce all genes that cold will. Conclusion: there are ABA-regulated and non-ABA regulated changes that are induced by cold.
Plants vary in ability to tolerate flooding Plants can be classified as: Wetland plants (e.g., rice, mangroves) Flood-tolerant (e.g., Arabidopsis, maize) Flood-sensitive (e.g., soybeans, tomato) Involves developmental/structural, cellular and molecular adaptations. Pneumatophores in mangrove
Flooding causes anoxia and an anaerobiotic response in roots. - Shift carbohydrate metabolism from respiration to anaerobic glycolysis - Protein synthesis affected: results in selective synthesis of ~10-20 proteins Maize (corn) Fig. 22.23
-mRNAs for other proteins there but not translated well! Most of the ANPs are enzymes associated with glycolysis and fermentation. Aerobic Anoxic Protein synthesis in aerobic versus anoxic maize root tips.
5-hour labeling with 3H-leucine and 2-D gel electrophoresis. Fig. 22.30 Enzymes that are upregulated by anaerobiosis Biotic Stress and Plant Defense Responses Pathogen Strategies 1. Necrotrophic plant tissue killed and then colonized; broad host range
e.g., rotting bacteria (Erwinia) 2. Biotrophic plant cells remain alive, narrow host range (1 plant species) e.g., viruses, nematodes, fungal mildews Major Pathogens Viruses - most are RNA viruses w/small genomes, which always encode: 1. Coat protein 2. RNA-dependent RNA polymerase 3. Movement protein(s)
SS RNA virus: Tobacco Mosaic Virus Viroids naked, single strands of RNA; discovered by T.O. Diener Bacteria- e.g., Xanthomonas Fungi - 4 major groups Nematodes - root parasites, also increase infection by microorganisms ds DNA virus:
Cauliflower Mosaic Virus Fig. 21.10, Buchanan et al. Plant Defenses 1) Physical barriers: cuticle, thorns, cell walls 2) Constitutively produced chemicals (e.g., phytoalexins) and proteins (e.g., Ricin) 3) Induced responses (a.k.a., the Plant Defense Response) The Plant Defense Response Compatible interaction disease
Incompatible interaction resistance 3 aspects of response: 1. Hypersensitive 2. Local 3. Systemic
Distribution of Oak Wilt in the US Leaves from Infected tree Fungus - Ceratocystis fagacearum Natural root grafts Sap beetle
"X" = X% chance of NOT exceeding the estimate. Example - You're on a project and your estimate is 8 person months. You've researched that 10% of similar projects have been under budget. p10 estimate = 7 staff months -...
OASIS New Section OPMT has Responsibility for OASIS OPMT may make changes to OASIS functionality CB OASIS Administrators Required When CB accreditation withdrawn, CBs client data only visible for 6 Months Created a Responsibility Matrix for data correctness Certification structures...
Malicious & Destructive Programs. Audit objectives: verify effectiveness of procedures to protect against programs such as viruses, worms, back doors, logic bombs, and Trojan horses. Audit procedures: review or verify… training of operations personnel concerning destructive programs. testing of new...
Posterior column-Medial lemniscus. 2nd order neurons synapse into the ventral posterior lateral (VPL) nucleus of the thalamus. 3rd order neurons then project to the posterior limb of the internal capsule to reach the primary somatosensory cortex in the post-central gyrus
Ohmic vs. non-ohmic devices Most materials obey Ohm's law at low temperatures, but as temperature increases, deviations from this law are seen. For example, an ordinary light bulb will obey Ohm's law as long as the current through it is...
You have access to CAR.ORG and you are familiar with and using Zipforms. ... Zipform will now automatically add a form if you check it in the RPA. ... (RR) will have WPA verbiage, seller's response is called the Seller...
consider how the PSC might work with agencies. to promote an integrated approach to workforce management, and in so doing, embed GSE reforms and deliver stronger business performance. Members of the PSC Advisory Board and people from the broader sector...
Ready to download the document? Go ahead and hit continue!