Root respiration associated with nitrogenase activity (c(2)h(2)) of soybean, and a comparison of estimates

Root respiration associated with symbiotic fixation in soybean (Glycine max [L.] Merr.) was estimated by four methods.

Averaged over the life of the plant, the root respires 5.8 milligrams C per milligram N accumulated from fixation. When nitrogenase (C₂H₂) activity and root respiration were decreased by treating roots briefly with 1.0 atmosphere O₂, the respiration associated with nitrogenase was estimated as 2.10 micromoles CO₂ per micromole C₂H₄.

When nitrogenase activity and respiration were decreased by addition of nitrate, the respiration associated with fixation was calculated as 2.90 micromoles CO₂ per micromole C₂H₄. Removing nodules from roots decreased fixation and root respiration, and the ratio was 4.08 micromoles CO₂ per micromole C₂H₄. When soybean plants were kept in prolonged darkness, then returned to light, the associated drop and recovery of respiration and nitrogenase activity had a ratio of 4.36 micromoles CO₂ per micromole C₂H₂.

     

Cardiovascular effects of prostaglandin D3 and D2 in anesthetized dogs

Prostaglandin (PG) D₃ has been identified as an inhibitor of human platelet aggregation, but little is known of the hemodynamic activity of this material. In morphine pretreated, chloralose-urethan anesthetized dogs, bolus intravenous injections (1, 3.2 and 10 μg/kg) of PGD₃ and also PGD₂ were associated with marked, dose-related increases in pulmonary arterial pressure. Cardiac index and rate increased, while peripheral vascular resistance decreased in response to injections of PGD₃. A biphasic (depressor followed by a pressor phase) effect on systemic arterial pressure was observed after PGD₂, while PGD₃ was associated with dose-related depressor responses. Graded intravenous infusions (0.25, 0.50 and 1.0 μg/kg/min) of PGD₃ and PGD₂ were associated with qualitatively similar cardiovascular responses. Quantitatively, PGD₃ infusions were associated with greater decreases in peripheral vascular resistance and greater increases in cardiac output, heart rate, and peak left ventricular dp/dt than were infusions of PGD₂. In contrast, PGD₃ was less potent than PGD₂ as a pulmonary pressor material. Systemic arterial pressure responses to infusions of the prostaglandins were variable. In these experiments, PGD₃ and PGD₂ were associated with qualitatively similar cardiovascular responses characterized by peripheral vasodilatation.     

Nitrogenase activity in the papyrus swamps of Lake Naivasha,Kenya

Nitrogenase activity (acetylene reduction activity) was found to occur universally in the Cyperus papyrus swamp in Lake Naivasha. Low rates of acetylene reduction activity (0.9–104.9 nmol C₂H₄ g d.wt. roots^-1 h^-1) were associated with excised roots of C. papyrus but higher rates of activity (89.0–280.4 nmol C₂H₄ g d.wt. roots^-1 h^-1) were associated with intact root systems of the plant. It was estimated that nitrogen fixation associated with young roots alone could supply about 26% of the nitrogen requirements of growing papyrus plants. Acetylene reduction activity in the lake bottom sediments was generally low and associated with adjacent papyrus stands. Plate counts of putative aerobic and facultatively anaerobic N₂-fixing bacteria associated with papyrus roots showed the presence of high numbers of diazotrophs (5.4 × 10⁶ CFU g d.wt. roots^-1). Fewer numbers of N₂-fixing bacteria were detected in the sediments (1.9 × 10³-3.2 × 10⁴ CFU g d.wt. sediment^-1).     

Design and synthesis of potential dual NK1/NK3 receptor antagonists

The tachykinin NK₁ and NK₃ receptors are a novel drug target for schizophrenia in order to treat not only the positive and cognitive symptoms, but also the associated co-morbid depression and sleep disturbances associated with the disease. A novel class of peptidomimetic derivatives based on a versatile phenylglycine central core was synthesized and tested in vitro as dual NK₁/NK₃ receptor antagonists. From this series emerged compounds with good NK₁ receptor affinity, although only modest dual NK₁/NK₃ receptor affinity was observed with one of these analogs.     

Associated growth of C3 and C4 desert plants helps the C3 species at the cost of the C4 species

C₃ desert plant Reaumuria soongorica (RS-C₃) and C₄ desert plant Salsola passerina (SP-C₄) may exist either in individual or in associated communities. Carbon isotope composition, leaf water potential, gas exchange and chlorophyll fluorescence characteristics of the individual and associated communities were compared with reveal, whether the associated growth represent an advantage under harsh habitat. The results showed that the ??¹³C values of leaves of RS-C₃ and SP-C₄ across different habitats fluctuated, respectively, from ?24 to ?27??? and from ?14 to ?16???. Leaf water potential of RS-C₃ was lower than SP-C₄ all day long, growing either individually or associated with the C₃ plant. When associated with the C₄ plant, the net photosynthetic rate of the RS-C₃ increased, and the photosynthetic rate of the partner SP-C₄ decreased. The transpiration rates of the associated RS-C₃ and SP-C₄ were both lower than in their individual colonies. In associated communities, in RS-C₃, the maximal photochemical efficiency, the effective photochemical efficiency, the relative electron transport rate, the photochemical quenching of PS II increased, and the non-photochemical quenching of PS II decreased; all these parameters changed oppositely in the SP-C₄ plant. This shows that, in the associated community, the C₄ plants might facilitate adaptation of the RS-C₃, while SP-C₄ plant can adapt to the harsh environment through their own specialties. The association favored the expression of natural photosynthetic characteristics and survival of RS-C₃, while retarded the growth of SP-C₄. Associated growth decreases the transpiration rate of the whole community; it is conducive to improve its water use efficiency.     

A Longitudinal Study of Sick Building Syndrome (SBS) among Pupils in Relation to SO2, NO2, O3 and PM10 in Schools in China

There are fewer longitudinal studies from China on symptoms as described for the sick building syndrome (SBS). Here, we performed a two-year prospective study and investigated associations between environmental parameters such as room temperature, relative air humidity (RH), carbon dioxide (CO₂), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), ozone (O₃), particulate matter (PM₁₀), and health outcomes including prevalence, incidence and remission of SBS symptoms in junior high schools in Taiyuan, China. Totally 2134 pupils participated at baseline, and 1325 stayed in the same classrooms during the study period (2010–2012). The prevalence of mucosal symptoms, general symptoms and symptoms improved when away from school (school-related symptoms) was 22.7%, 20.4% and 39.2%, respectively, at baseline, and the prevalence increased during follow-up (P<0.001). At baseline, both indoor and outdoor SO₂ were found positively associated with prevalence of school-related symptoms. Indoor O₃ was shown to be positively associated with prevalence of skin symptoms. At follow-up, indoor PM₁₀ was found to be positively associated with new onset of skin, mucosal and general symptoms. CO₂ and RH were positively associated with new onset of mucosal, general and school-related symptoms. Outdoor SO₂ was positively associated with new onset of skin symptoms, while outdoor NO₂ was positively associated with new onset of skin, general and mucosal symptoms. Outdoor PM₁₀ was found to be positively associated with new onset of skin, general and mucosal symptoms as well as school-related symptoms. In conclusion, symptoms as described for SBS were commonly found in school children in Taiyuan City, China, and increased during the two-year follow-up period. Environmental pollution, including PM₁₀, SO₂ and NO₂, could increase the prevalence and incidence of SBS and decrease the remission rate. Moreover, parental asthma and allergy (heredity) and pollen or pet allergy (atopy) can be risk factors for SBS.     

Role of lipoxygenase metabolism in platelet function: Effect of aspirin and salicylate

Aspirin inhibits thromboxane A₂ (TxA₂) production whereas its salicylate moiety inhibits 12-hydroxy-eiosatetraenoic acid (12-HETE) production in the platelet. The significance of the latter effect on platelet function is unclear. We examined the effects of aspirin and salicylate on (i) platelet/ collagen adhesion using ³H-adenine-labelled human platelets and collagen- coated discs, (ii) platelet aggregation induced by thrombin, collagen, ADP and arachidonic acid, and (iii) platelet TxA₂ and 12-HETE synthesis as measured by radioimmunoassay and high pressure liquid chromatography respectively. Aspirin (50 μM) decreased platelet aggregation and increased platelet adhesion. The decrease in aggregation was associated with inhibition of TxA₂ production and the increase in adhesion was associated with enhanced 12-HETE production. Salicylate had the opposite effects. Platelet aggregation was increased and platelet adhesion decreased. The increased aggregation was associated with enhanced TxA₂ production and the decrease in aggregation was associated with inhibition of 12-HETE production. These observations suggest that 12-HETE facilitates platelet adhesion which can be altered by salicylate treatment.     

Effects of two estradiol regimens on anxiety and depressive behaviors and trophic effects in peripheral tissues in a rodent model

Background: With aging and menopause, which are associated with decreases in ovarian steroids such as 17β-estradiol (E₂), women might experience negative psychological symptoms, including anxiety and depression. Some women use E₂-based therapies to alleviate these symptoms, but E₂ has been associated with trophic effects that might increase vulnerability to some steroid-sensitive cancers, such as breast cancer, in both premenopausal and postmenopausal women.Objective: This study investigated the relationships between the possible beneficial effects of E₂ on anxiety and depressive behaviors concurrent with trophic effects using an animal model of E₂ decline and replacement.Methods: Dose-dependent effects of E₂ on affective, sexual, and motor behavior of young adult rats were studied. Ovariectomized (OVX) rats were administered the chemical carcinogen 7,12-dimethylbenz(a) anthracene (DMBA) 1.25 mg or inactive vehicle (vegetable oil; control) by gavage. E₂ (0.03 or 0.09 mg/kg) or vehicle was administered subcutaneously 44 to 48 hours before assessments of anxiety (light—dark transition), depression (forced swim test), sexual (lordosis), and motor (activity monitor) behaviors. Fourteen weeks after carcinogen exposure, E₂ concentrations in plasma and brain regions (cortex, hippocampus, and hypothalamus) were determined. Incidences and numbers of tumors and uterine weight were analyzed.Results: Administration of E₂ (0.09 mg/kg) was associated with significant increases in antianxiety-like behavior in the light—dark transition task, antidepressant-like behavior in the forced swim test, and physiologic circulating and central E₂ concentrations compared with E₂ (0.03 mg/kg) and vehicle. Compared with vehicle, E₂ (0.9 > 0.3 mg/kg) was associated with significant increases in lordosis and uterine weight. Administration of DMBA was associated with significant increases in the incidences and numbers of tumors; this effect was augmented by E₂administration.Conclusions: Based on the findings in this rat model, the hypothesis that E₂ may be effective in reducing anxiety and depressive behaviors and enhance sexual behavior in OVX rats, concurrent with trophic effects in the periphery, was supported. Moderate physiologic levels of E₂ might have beneficial effects on affective and sexual behaviors in female rodents, but regimens including E₂ might increase tumorigenic capacity.     

Nitrogen Fixation Associated with Sand Grain Root Sheaths (Rhizosheaths) of Certain Xeric Grasses

Nitrogen fixation (acetylene reduction) was found to be associated with sand grain root sheaths (rhizoseaths) occurring on the following xeric grasses: Oryzopsis hymenoides (Roem. and Shult.) Ricker, Agropyron dasystachyum (Hook.) Scrib., Stipa comata Trin. and Rupr., and Aristida purpurea Nutt. Acetylene reduction rates associated with whole plant specimens of these species varied from 515 to 920 nmol C₂H₄/(g dry wt.) × (6 days). Nitrogenase activity was shown to be associated with the rhizosheaths. Bacillus polymyxa-like nitrogen fixers were isolated from the rhizosheaths of each grass. The isolates reduced acetylene and assimilated ¹⁵N₂.     

Impact of soil environmental factors on rates of N2-fixation associated with roots of intact maize and sorghum plants

We have evaluated the effects of oxygen partial pressure (pO₂), combined nitrogen, and the availability of organic substrates on nitrogen fixation (acetylene reduction) by bacteria associated with the roots of intact maize and sorghum plants. We also investigated the possibility of enhancing associative nitrogen-fixation by inoculating the soil in which the plants were grown withAzospirillum. Acetylene reduction (AR) activity was greatest when roots of intact plants were exposed to pO₂ between 1.3 and 2.1 kPa. Field-grown and greenhouse-grown plants supported similar levels of activity. Respiration inhibitors (2,4-dinitrophenol and sodium azide) eliminated AR activity at 2 kPa O₂, whereas a fermentation inhibitor (sodium fluoride) only partially reduced the activity. Acetylene reduction activity was rapidly (1–3 h) inhibited by NH ₄ ⁺ , NO ₃ ^– , and NO ₂ ^– at concentrations of 4–20 mg Nl^–1. Rates of AR varied substantially among individual plants in each experiment and between experiments. Amendment with any of several organic substrates greatly increased AR activity when rates were low, suggesting that the lack of activity was caused by a shortage of available carbon in the rhizosphere. Inoculation withAzospirillum failed to increase rates of AR associated with maize plants. In several experiments the indigenous bacteria associated with uninoculated plants exhibited greater activity than the bacteria associated with inoculated plants.     

Role of protein kinase C in oxidant — mediated activation of phospholipase A2 in rabbit pulmonary arterial smooth muscle cells

The present study was undertaken to test the hypothesis that activation of cell membrane associated protein kinase C (PKC) plays a role in stimulating cell membrane associated phospholipase A₂ (PLA₂) activity, and subsequent liberation of arachidonic acid (AA) under exposure of rabbit pulmonary arterial smooth muscle cells to the oxidant hydrogen peroxide (H₂O₂). Exposure of the smooth muscle cells to H₂O₂ dose-dependently stimulates [¹⁴C] AA release, and enhances the cell membrane associated PLA₂ activity. Pretreatment of the cells with protein kinase C (PKC) inhibitors H₇ and sphingosine prevent the cell membrane associated PLA₂ activity, and AA release caused by H₂O₂. Treatment of the smooth muscle cells with H₂O₂ stimulates the cell membrane associated PKC activity. Pretreatment of the cells with an antioxidant vitamin E prevents H₂O₂ caused stimulation of the cell membrane associated PKC activity. The cell membrane associated PLA₂ and PKC activities correlate linearly. These results suggest that H₂O₂ caused stimulation of the smooth muscle cell membrane associated PLA₂ activity, and subsequent liberation of AA can occur through an increase in the activity of the cell membrane associated PKC. (Mol Cell Biochem122: 9–15, 1993)Abbreviations AA Arachidonic Acid - PLA₂ Phospholipase A₂ - PKC Protein Kinase C - PBS Phosphate Buffered Saline - HBPS Hank's Buffered Physiological Saline - HEPES 4-(2-Hydroxyethyl)-1-Piperazine N-2-Ethanesulfonate - FCS Fetal Calf Serum - ATP Adenosine Triphosphate - H₇ 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine - DMEM Dulbecco's Modified Eagles Medium - TCA Trichloroacetic Acid     

Insulin protects H9c2 rat cardiomyoblast cells against hydrogen peroxide-induced injury through upregulation of microRNA-210

Abstract

Background. Insulin protects cardiomyocytes from reactive oxygen species (ROS)-induced apoptosis after ischemic/reperfusion injury, but the mechanism is not clear. This study investigated the protective mechanism of insulin in preventing cardiomyocyte apoptosis from ROS injury. Methods. Rat cardiomyoblast H9c2 cells were treated with hydrogen peroxide (H₂O₂) or insulin at various concentrations for various periods of time, or with insulin and H₂O₂ for various periods of time. Cell viability was measured by the methylthiazolydiphenyl-tetrazolium bromide method. Cellular miR-210 levels were quantified using real-time RT-PCR. MiR-210 expression was also manipulated through lentivirus-mediated transfection. LY294002 was used to investigate involvement of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Results. The percentage of viable cells was significantly and inversely associated with H₂O₂ concentration, an effect that was seemingly attenuated by insulin pretreatment. Treatments with H₂O₂ or insulin were associated with a significant increase in miR-210 levels. Manipulation of miR-210 expression by gene transfection showed that miR-210 could attenuate H₂O₂-induced cellular injury. Inhibition of the PI3K/Akt pathway by the Akt inhibitor LY294002 was associated with a decrease in miR-210 expression. Conclusion. Insulin stimulated the expression of miR-210 through the PI3K/Akt pathway, resulting in a protective effect against cardiomyocyte injury that had been induced by H₂O₂/oxygen species. Our results provide novel evidence regarding the mechanism underlying the protective effect of insulin.     

Reversible conjugation of gibberellins in situ in maize

Gibberellins [³H]GA₄ (1.33 Curies per millimole) and [³H]GA₂₀ (2.36 Curies per millimole) were injected into the shanks of maize (Zea mays L.) cobs during rapid grain filling and mature seeds were subsequently harvested. Extracts of mature, dry seeds from 1980 feeds yielded only 20 to 30% of the ³H radioactivity in acidic, ethyl acetate-soluble form, and this was principally associated with the precursor, with lesser amounts of the major metabolite, [³H]GA₁ (putative identification based on sequential SiO₂ partition, and gradient-eluted reverse-phase C₁₈ high performance liquid chromatography [HPLC]). Most of the radioactivity in the dry seeds was associated with compounds having partition characteristics of, and co-chromatographing on, sequential SiO₂ partition and reverse-phase HPLC with glucosyl conjugates of the precursors (GA₄ or GA₂₀) and their probable major metabolite (GA₁). The majority of conjugate associated with the precursor GA₄ eluted coincidental with GA₄ glucoside. Subsequent acid or enzymic hydrolysis (β-glucosidase or cellulase) yielded the free GAs, putative identification being based on isocratic HPLC of each ³H-labeled conjugate → hydrolysis → isocratic HPLC of the ³H-labeled hydrolysate. Upon imbibition of the seeds, radioactivity associated with the conjugate fraction decreased; concomitantly, statistically significant increases in levels of free [³H]GA-like compounds were observed. Although the specific ratios of GA-like and GA-glucosyl conjugate-like substances varied substantially across years, hybrids, and even, in different plants from the same hybrid, this `reversible conjugation' (i.e. apparent conjugation during seed maturation followed by release of the GA moiety during germination), was reproducible for [³H]GA₂₀ in seed from two maize hybrids produced over 2 years.     

Nitrogen-Fixing (Acetylene Redution) Activity and Population of Aerobic Heterotrophic Nitrogen-Fixing Bacteria Associated with Wetland Rice

Nitrogen-fixing activity associated with different wetland rice varieties was measured at various growth stages by an in situ acetylene reduction method after the activities of blue-green algae (cyanobacteria) in the flood water and on the lower portion of the rice stem were eliminated. Nitrogen-fixing activities associated with rice varieties differed with plant growth stages. The activities increased with plant age, and the maximum was about at heading stage. The nitrogen fixed during the whole cropping period was estimated at 5.9 kg of N per ha for variety IR26 (7 days) and 4.8 kg of N per ha for variety IR36 (95 days). The population of aerobic heterotrophic N₂-fixing bacteria associated with rice roots and stems was determined by the most-probable-number method, using semisolid glucose-yeast extract and semisolid malate-yeast extract media. The addition of yeast extract to the glucose medium increased the number and activity of aerobic heterotrophic N₂-fixing bacteria. The glucose-yeast extract medium gave higher counts of aerobic N₂-fixing bacteria associated with rice roots than did the malate-yeast extract medium, on which Spirillum-like bacteria were usually observed. The lower portion of the rice stem was also inhabited by N₂-fixing bacteria and was an active site of N₂ fixation.     

Light-dependent reduction of dehydroascorbate by ruptured pea chloroplasts

Glutathione dehydrogenase (EC 1.8.5.1) was partially purified from pea shoots. The pH optimum was 7.6. The K_m values for GSH and dehydroascorbate were 4.4 and 0.44 millimolar, respectively. The enzyme was inhibited by iodoacetate and CuSO₄ but not significantly by ZnCl₂ or NaN₃. Part of the total enzyme activity was associated with isolated chloroplasts.     

Experimental determination of the respiration associated with soybean/rhizobium nitrogenase function, nodule maintenance, and total nodule nitrogen fixation

The total metabolic cost of soybean (Glycine max L. Mer Clark) nodule nitrogen fixation was empirically separated into respiration associated with electron flow through nitrogenase and respiration associated with maintenance of nodule function.

Rates of CO₂ evolution and H₂ evolution from intact, nodulated root systems under Ar:O₂ atmospheres decreased in parallel when plants were maintained in an extended dark period. While H₂ evolution approached zero after 36 hours of darkness at 22°C, CO₂ evolution rate remained at 38° of the rate measured in light. Of the remaining CO₂ evolution, 62% was estimated to originate from the nodules and represents a measure of nodule maintenance respiration. The nodule maintenance requirement was temperature dependent and was estimated at 79 and 137 micromoles CO₂ (per gram dry weight nodule) per hour at 22°C and 30°C, respectively.

The cost of N₂ fixation in terms of CO₂ evolved per electron pair utilized by nitrogenase was estimated from the slope of H₂ evolution rate versus CO₂ evolution rate. The cost was 2 moles CO₂ evolved per mole H₂ evolved and was independent of temperature.

In this symbiosis, nodule maintenance consumed 22% of total respiratory energy while the functioning of nitrogenase consumed a further 52%. The remaining respiratory energy was calculated to be associated with ammonia assimilation, transport of reduced N, and H₂ evolution.

     

The association of thromboxane A2 receptor with lipid rafts is a determinant for platelet functional responses

We have investigated the presence of thromboxane A₂ (TXA₂) receptor associated with lipid rafts in human platelets and the regulation of platelet function in response to TXA₂ receptor agonists when lipid rafts are disrupted by cholesterol extraction. Platelet aggregation with TXA₂ analogs U46619 and IBOP was almost blunted in cholesterol-depleted platelets, as well as α_IIbβ₃ integrin activation and P-selectin exposure. Raft disruption also inhibited TXA₂-induced cytosolic calcium increase and nucleotide release, ruling out an implication of P2Y₁₂ receptor. An important proportion of TXA₂ receptor (40%) was colocalized at lipid rafts. The presence of the TXA₂ receptor associated with lipid rafts in platelets is important for functional platelet responses to TXA₂.     

Inhibition of Nitrate Transport by Anti-Nitrate Reductase IgG Fragments and the Identification of Plasma Membrane Associated Nitrate Reductase in Roots of Barley Seedlings

Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots. The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity. PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold. The latency was a function of the solubilization of NR from the membrane. NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR. Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO₃⁻ uptake by more than 90% but had no effect on NO₂⁻ uptake. The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots. Preimmune serum immunoglobulin G fragments inhibited NO₃⁻ uptake 36% but the effect was completely reversible by rinsing. Intact NR antiserum had no effect on NO₃⁻ uptake. The results present the possibility that NO₃⁻ uptake and NO₃⁻ reduction in the PM of barley roots may be related.     

Characterization and fine-mapping of a resistance locus for northern leaf blight in maize bin 8.06

As part of a larger effort to capture diverse alleles at a set of loci associated with disease resistance in maize, DK888, a hybrid known to possess resistance to multiple diseases, was used as a donor in constructing near-isogenic lines (NILs). A NIL pair contrasting for resistance to northern leaf blight (NLB), caused by Setosphaeria turcica, was identified and associated with bin 8.06. This region of the maize genome had been associated in previous studies with both qualitative and quantitative resistance to NLB. In addition, bins 8.05–8.06 had been associated with quantitative resistance to several other diseases, as well as resistance gene analogs and defense response gene homologs. To test the hypothesis that the DK888 allele at bin 8.06 (designated qNLB8.06 _DK888 ) conditions the broad-spectrum quantitative resistance characteristic of the donor, the NILs were evaluated with a range of maize pathogens and different races of S. turcica. The results revealed that qNLB8.06 _DK888 confers race-specific resistance exclusively to NLB. Allelism analysis suggested that qNLB8.06 _DK888 is identical, allelic, or closely linked and functionally related to Ht2. The resistance conditioned by qNLB8.06 was incompletely dominant and varied in effectiveness depending upon allele and/or genetic background. High-resolution breakpoint analysis, using ~2,800 individuals in F₉/F₁₀ heterogeneous inbred families and 98 F₁₀/F₁₁ fixed lines carrying various recombinant events, delimited qNLB8.06 _DK888 to a region of ~0.46 Mb, spanning 143.92–144.38 Mb on the B73 physical map. Three compelling candidate genes were identified in this region. Isolation of the gene(s) will contribute to better understanding of this complex locus.