Complex Iron Sulfur Subunit Research Articles

Differential profiles of membrane proteins, fatty acids, and sterols associated with genetic variations in heat tolerance for a perennial grass species, hard fescue (Festuca Trachyphylla)

Cellular membrane composition controls membrane stability, affecting plant tolerance to abiotic stress. The objectives of this study were to examine differential changes in membrane constituents (sterol, fatty acid and membrane protein) in response to heat stress for a cool-season perennial grass species, hard fescue (Festuca trachyphylla) and identify major membrane constituents associated with the genetic variations in heat tolerance for two varieties contrasting in heat tolerance. Plants of heat-tolerant ‘Reliant IV’ and heat-sensitive ‘Predator’ were exposed to heat stress at 38/33°C (day/night) in growth chambers. Under heat stress, ‘Reliant IV’ showed better turf quality, greater membrane stability and higher photochemical efficiency compared to ‘Predator’. Leaf membranes of ‘Reliant IV’ showed greater increase of ethyl sterols (fucosterol, stigmasterol, sitosterol and avenasterol), and two fatty acids [oleic acid (18:1) and linoleic acid (18:2)] under heat stress compared to those for ‘Predator’. Several membrane proteins were less down-regulated or more up-regulated by heat stress in ‘Reliant IV’ than in ‘Predator’, including down-regulated proteins involved in electron transport of photosynthesis (ATP synthase subunits and cytochrome b6-f complex iron-sulfur subunit), signaling (lectin-domain containing receptor kinase A4.2), and protein modification (S-acyltransferase), and up-regulated proteins involved in carboxylation in photosynthesis (Rubisco activase beta form) and stress defense (disease resistance protein 1). These differentially accumulated sterols, fatty acids, and proteins in cellular membranes could contribute to the differential level of heat tolerance between the two varieties of hard fescues. These compounds could be used as biomarkers to select for heat-tolerant germplasm in hard fescues.

Paraganglioma of the organ of Zuckerkandl associated with a somatic HIF2α mutation: A case report.

Paragangliomas of the organ of Zuckerkandl (OZ-PGL) are rare tumors that, in >70% of cases, occur in association with succinate dehydrogenase complex iron sulfur subunit B (SDHB) or SDHD gene mutations. The aim of the current study was to determine whether a somatic genetic defect in the hypoxia-inducible factor 2α (HIF2α) gene was present in a case of sporadic OZ-PGL. A 32-year-old African female presented with uncontrolled hypertension during the first trimester of pregnancy. A diagnostic hysteroscopy was performed 3 months after delivery, precipitating a hypertensive crisis. Thereafter, the patient was diagnosed with noradrenaline-secreting OZ-PGL. A complete blood count identified mild normocytic anemia of an inflammatory origin. Surgical removal of the tumor resulted in normalization of plasma and urinary normetanephrine levels. Genetic testing for germline mutations (including large deletions) in the von Hippel-Lindau tumor suppressor, SDHB, SDHC and SDHD genes was normal. However, a heterozygous missense mutation (c.1589Cys>Tyr) was detected in exon 12 of HIF2α, which results in a substitution of alanine 530 with valine (Ala530Val) in the HIF2α protein. A germline mutation was excluded based on the negative results of blood DNA testing. A three-dimensional homology model of Ala530Val was constructed, which showed impaired HIF2α/VHL interaction and decreased HIF2α ubiquitination. 1H-high-resolution magic-angle-spinning nuclear magnetic resonance spectroscopy detected low succinate levels and high α and β glucose levels. To the best of our knowledge, the present case represents the first of its kind to associate a somatic HIF2α gain-of-function mutation with OZ-PGL. It is therefore recommended that patients without germline SDHx mutations should be tested for HIF2α mutations.

Effects of As stress on contents of saponin and flavonoid, key enzymes activities of Panax notoginseng and its proteomic analysis

Field plot experiments were conducted to study the effect of two-year consecutive As stress [As(V): 0, 20, 80, 140, 200 and 260 mg·kg-1] on contents of As, saponin and flanovoids, the enzyme activities of phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), and squalene synthase (SS) in main root, fibrous root and rhizome and shoot, and proteome of three-year old Panax notoginseng in Wenshan prefecture, Yunnan Province, China. The results showed that total saponin content of fibrous root decreased with increase in As treatment concentration. Total saponin contents of shoot and rhizome increased with 140 mg·kg-1 As treatment compared with control. SS activity of rhizome was higher than that of shoot. Flavonoid contents of diffe-rent plant parts decreased with increase in As treatment concentration. With 140 mg·kg-1 As treatment, activities of PAL and CHS in rhizome were higher than that in shoot. CHS activities in shoot and rhizome were lower, and PAL activities were higher than those of the control. As contents in different plant parts of P. notoginseng increased with increase in As treatment concentration. The highest As content was observed in fibrous root. With 140 mg·kg-1 As treatment, twenty-one diffe-rential proteins (ratio >2, P<0.05) were identified in the inoculated compared to the control. The down-regulated proteins included phosphoribulokinase, heat shock protein, NAD(P)-binding rossmann-fold superfamily proteinisoform, monodehydroascorbate reductase and cytochrome b6-f complex iron-sulfur subunit. The up-regulated proteins included CDC27 family protein, acidic endochitinase isoform, symbiosis receptor-like kinase precursor, isoflavone reductase-like protein, phospho-2-dehydro-3-deoxyheptonate aldolase, putative protein kinase superfamily protein, malate dehydrogenase, glyoxalase I isoform and glutamine synthetase cytosolic isozyme. In general, with two-year consecutive As stress, As contents in different plant parts of P. notoginseng increased, which not only affected the photosynthesis and energy, but also decreased the antioxidation and resilience, and induced the increased expression of protein involved in detoxication, resulted in decrease in the contents of flavonoid and saponin. The tolerant threshold value of P. notoginseng for As was 140 mg·kg-1.

Characterization of Small Heat Shock Proteins Associated with Maize Tolerance to Combined Drought and Heat Stress

To investigate how the mechanisms of small heat shock proteins (sHSPs) in regulating maize leaves respond to the combination of drought and heat stress, leaf protein patterns were monitored using a proteomic approach in maize plants exposed to combined drought and heat stress. Two-dimensional electrophoresis (2-DE) was used to identify combined drought- and heat-responsive protein spots in maize leaves. After Coomassie brilliant blue staining, approximately 450 protein spots were reproducibly detected on each gel, wherein 7 protein spots were expressed only under heat and combined drought and heat stress but were almost undetected under control and drought. Using MALDI-TOF mass spectrometry, a total of seven proteins were identified, including cytochrome b6-f complex iron-sulfur subunit, sHSP17.4, sHSP17.2, sHSP26, guanine nucleotide-binding protein β-subunit-like protein, putative uncharacterized protein, and granule-bound starch synthase IIa. Moreover, the gene expression of three sHSPs was analyzed at the transcriptional level and indicated that all three sHSPs were expressed under several treatments although their expression levels were obviously more enhanced by heat and combined drought and heat stress than by control and drought. In investigations of the effect of abscisic acid (ABA) on the three sHSPs, pretreatment with 100 μM ABA enhanced substantially the expression of the three sHSPs at the protein level, but only slightly at the mRNA level. These results show that transcription levels are not completely concomitant with translation and suggest that ABA induces the post-transcriptional regulation of sHSP17.2, sHSP17.4, and sHSP26 expression, which can lead to a better understanding of the mechanisms of plant response to the combination of drought and heat stress.