Shavannor Smith

University of Georgia | UGA · Department of Plant Pathology

Key message This manuscript provides genome-level analysis of disease resistance genes in four maize lines, including studies of haplotype and resistance gene number as well as selection and recombination. Abstract The Rp1 locus of maize is a complex resistance gene (R-gene) cluster that confers race-specific resistance to Puccinia sorghi, the c...

Maize is a major cereal crop worldwide. However, susceptibility to biotrophic pathogens is the primary constraint to increasing productivity. U. maydis is a biotrophic fungal pathogen and the causal agent of corn smut on maize. This disease is responsible for significant yield losses of approximately $1.0 billion annually in the U.S.(1) Several met...

Resistance Gene Homologues (RGHs) were isolated from the switchgrass variety Alamo by a combination of PCR and expressed sequence tag (EST) database mining. Fifty-eight RGHs were isolated by PCR and 295 RGHs were identified in 424,545 switchgrass ESTs. Four NBS-LRR RGHs were selected to investigate RGH haplotypic diversity in seven switchgrass vari...

Tef (Eragrostis tef) is a major cereal crop in Ethiopia. Lodging is the primary constraint to increasing productivity in this allotetraploid species, accounting for losses of ~15-45% in yield each year. As a first step toward identifying semi-dwarf varieties that might have improved lodging resistance, an ~6X fosmid library was constructed and used...

Eragrostis tef (Zucc.), a member of the Chloridoideae subfamily of grasses, is one of the most important food crops in Ethiopia. Lodging is the most important production problem in tef. The rht1 and sd1 dwarfing genes have been useful for improving lodging resistance in wheat and rice, respectively, in what has been known as the "Green Revolution."...

Genes at the Rp1 rust resistance locus of maize confer race-specific resistance to the common rust fungus Puccinia sorghi. Three variant genes with nonspecific effects (HRp1 -Kr1N, -D*21 and -MD*19) were found to be generated by intragenic crossing over within the LRR region. The LRR region of most NBS-LRR encoding genes is quite variable and codes...

Genes at the maize Rp1 rust resistance complex often mispair in meiosis, which allows genes to recombine unequally, creating recombinant haplotypes. Four recombinant haplotypes were identified from progeny of an Rp1-D/Rp1-I heterozygote that conferred a nonparental resistance specificity designated Rp1-I*. Sequence comparisons of paralogs in the re...

The maize Rp1 rust resistance locus is a complex consisting of a family of closely related resistance genes. The number of Rp1 paralogs in different maize lines (haplotypes) varied from a single gene in some stocks of the inbred A188 to >50 genes in haplotypes carrying the Rp1-A and Rp1-H specificities. The sequences of paralogs in unrelated haplot...

Recent data indicate that bilateral carotid sinus denervation in patients results in a chronic impairment in the rapid reflex control of blood pressure during orthostasis. These findings are inconsistent with previous human experimental investigations indicating a minimal role for the carotid baroreceptor-cardiac reflex in blood pressure control. T...

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cu...

1. This investigation was designed to determine the contribution of central command to the resetting of the carotid baroreflex during static and dynamic exercise in humans. 2. Thirteen subjects performed 3.5 min of static one-legged exercise (20 % maximal voluntary contraction) and 7 min dynamic cycling (20 % maximal oxygen uptake) under two condit...

1. This investigation was designed to determine the contribution of the exercise pressor reflex to the resetting of the carotid baroreflex during exercise. 2. Ten subjects performed 3.5 min of static one-legged exercise (20 % maximal voluntary contraction) and 7 min dynamic cycling (20 % maximal oxygen uptake) under two conditions: control (no inte...

Rp1 is a complex rust resistance locus of maize. The HRp1-D haplotype is composed of Rp1-D and eight paralogues, seven of which also code for predicted nucleotide binding site-leucine rich repeat (NBS-LRR) proteins similar to the Rp1-D gene. The paralogues are polymorphic (DNA identities 91-97%), especially in the C-terminal LRR domain. The remaini...

In order to characterize the stimulus-response relationships of the arterial, aortic, and carotid baroreflexes in mediating cardiac chronotropic function, we measured heart rate (HR) responses elicited by acute changes in mean arterial pressure (MAP) and carotid sinus pressure (CSP) in 11 healthy individuals. Arterial (aortic + carotid) baroreflex...

Transmission characteristics of pneumatic pressure to the carotid sinus were evaluated in 19 subjects at rest and during exercise. Either a percutaneous fluid-filled (n = 12) or balloon-tipped catheter (n = 7) was placed at the carotid bifurcation to record internal transmission of external neck pressure/neck suction (NP/NS). Sustained, 5-s pulses,...

This investigation was designed to determine central command's role on carotid baroreflex (CBR) resetting during exercise. Nine volunteer subjects performed static and rhythmic handgrip exercise at 30 and 40% maximal voluntary contraction (MVC), respectively, before and after partial axillary neural blockade. Stimulus-response curves were developed...

More than 30 genes have been characterized from different plant species that provide resistance to a variety of different pathogen and pest species. The structures of most are consistent with a role in pathogen recognition and defense response signaling. Resistance genes are very abundant in plant genomes and most belong to tightly linked gene fami...

We compared arterial, aortic, and carotid-cardiac baroreflex sensitivity in eight average fit (maximal oxygen uptake, VO2max = 42.2+/-1.9 mL x kg(-1) x min(-1)) and eight high fit (VO2max = 61.9+/-2.2 mL x kg(-1) x min(-1)) healthy young adults. Arterial and aortic (ABR) baroreflex functions were assessed utilizing hypo- and hyper-tensive challenge...

The present investigation was designed to uncouple the hemodynamic physiological effects of thermoregulation from the effects of a progressively increasing central command activation during prolonged exercise. Subjects performed two 1-h bouts of leg cycling exercise with 1) no intervention and 2) continuous infusion of a dextran solution to maintai...

Eight subjects, aged 27.0+/-1.6 yr, performed incremental workload cycling to investigate the contribution of skeletal muscle mechano- and metaboreceptors to ventilatory control during dynamic exercise. Each subject performed four bouts of exercise: exercise with no intervention (CON); exercise with bilateral thigh cuffs inflated to 90 mm Hg (CUFF)...

Six average fit (26 ± 2 yrs; V̇O2peak = 38 ± 1 ml·kg-1·min-1) subjects performed dynamic cycling to determine if increases or decreases in venous return affect the plateau that occurs in stroke volume during dynamic exercise. Each subject performed three bouts of exercise to volitional fatigue: control; exercise with Lower Body Negative Pressure (L...

The purpose of this study was to test the hypothesis that low-frequency (LF) oscillation of systolic arterial pressure (SP) during central hypovolemia was less resposive with aging. Beat to beat SP (intra-arterial catheter or Finapres) and HR in 9 young (Y ≤30yrs) and 7 older (O ≥60yrs) healthy subjects were collected during supine resting, lower b...

Five endurance trained (ET; 62 V̇O2max; 4 men/1 women) and five untrained (UT; 36 V̇O2max; 3 men/2 women) young adults performed incremental exercise on a cycle ergometer to volitional fatigue. Heart rate (HR; beats·min-1), cardiac output (Q̇c; L·min-1), V̇O2 (ml·kg-1·min-1) were measured and stroke volume (SV; ml·beat-1) was calculated (mean±SEM)...

Eight subjects, aged 26.5 ± 3.7 yrs, performed incremental workload cycling to investigate the interaction of skeletal muscle ergoreceptors in eliciting a ventilatory stimulus response to exercise. Each subject performed three bouts of exercise: control (exercise - no intervention); exercise with thigh cuff inflation to 90 mmHg (to reduce venous ou...

The aim of this study was to test the hypothesis that cardiopulmonary baroreflex control of forearm vascular resistance (FVR) during central hypervolemic loading was less sensitive in exercise trained high fit individuals (HF) compared to untrained average fit individuals (AF). Eight AF (age: 24 +/- 1 yr and weight: 78.9 +/- 1.7 kg) and eight HF (2...