Chrysemys picta
Sex chromosomes

Dr. Nicole Valenzuela, Iowa State University



Open Graduate Student Positions

Multiple graduate positions are currently open

I am looking for motivated and talented PhD students to work on various projects in my lab as described below. Students are welcome to develop independent projects within these areas or in complementary areas in evolutionary biology, sex determination, evo-devo, chromosome evolution, genomics and epigenetics, using turtles or other taxa.

Evolution of dosage compensation using turtles


Species with sex chromosomes face the challenge posed by differential gene dosage between XX and XY individuals (or ZZ and ZW) that may lead to disease, suboptimal phenotypes or death. Dosage compensation is a mechanism to equalize the activity of X- or Z-linked genes between sex chromosomes and autosomes, and between males and females. As part of this NSF-funded project we are leveraging the multiple inpendently-evolved sex chromosome systems ini turtles to study the evolution of dosage compensation. Students interested in exploring the full diversity of dosage compensation mechanisms and their molecular underpinnings will have the opportunity to contrast turtles with alternative sex-determining mechanisms, leveraging and augmenting the genomic resources available for this group.

Co-evolution of chromosome number and sex determination


We recently discovered that the turtles lineages that underwent a transition in the sex determination also suffered a drastic increase in the rate of evolution of chromosome number, but it is unclear why or how these traits are associated. As part of an NSF-funded PhyloGenomics project (MCB 1244355) we are studying the genome rearrangements responsible for the changes in diploid number across turtles and their association with transitions in sex determination. Students interested in this area will have the opportunity to work on molecular cytogenetics, transcriptomics, bioinformatics and phylogenetics, to understand how chromosomal rearrangements disrupt the location and regulation of genes controlling sexual development.

Responses of sex determination to climate change

Climate change is expected to cause a decline of global biodiversity as it exposes organisms to great environmental fluctuations to which they must respond adaptively to persist. TSD species are especially challenged because changes in environmental temperature can profoundly alter their sex ratio and many TSD species are endangered. Students interested in this area will participate in our ongoing projects using transcriptomic and epigenomic approaches to study the genetic and epigenetic responses of TSD and GSD turtles under climate change scenarios. This continues our extensive work in this area facilitated by an NSF grant (Developmental Systems IOS 0743284 “Gene expression response to naturally fluctuating temperature in turtles with alternative sex determining mechanisms”).

Local adaptation of sex determination across geographic gradients

Understanding the genetic architecture underlying adaptation is critical in evolutionary and conservation biology. Central to this is understanding adaptation in geographically heterogeneous environments, particularly for widespread taxa that are susceptible to global environmental change as is the case of TSD species. Students interested in this area will have the opportunity to work with widely distributed turtles to uncover how their sex-determining mechanism has adapted to local conditions across their geographic range, and what is their genome-wide evolutionary potential, using and augmenting the turtle genomic resources we have developed.

Prospective students apply to one of ISU's graduate programs

Depending on their interests and background, students could apply to one of the following graduate programs at ISU.

(1) Ecology and Evolutionary Biology

(2) Bioinformatics and Computational Biology

(3) Interdepartmental Genetics and Genomics.

All prospective students must take the GRE General Test.

International students whose native language is not English must take the TOEFL or IELTS.

Interested candidates should contact Dr. Nicole Valenzuela at nvalenzu@iastate.edu to discuss their interests and funding options.

Open Internships for Undergraduates

Internships for undergraduate students are available through the Iowa Turtle Army program in my lab. For details please visit the Iowa Turtle Army's Website

Open Opportunities for Postdoctoral Research Associates

Opportunities for Independent Postdoctoral Research

Interested postdocs are welcome to develop their own grant proposals that will provide them independent funding to carry out collaborative research in our lab.

For inquiries please email Dr. Nicole Valenzuela at nvalenzu@iastate.edu to discuss potential research projects of common interest.

Applicants should email a cover letter describing their research interests and experience, current CV, and copies of up to two relevant publications if available.

Postdoctoral Research Opportunities for Groups Under-represented in Biology

NSF-funded Postdoctoral Research Fellowships in Biology (PRFB). Interested postdocts should contact Dr. Nicole Valenzuela at nvalenzu@iastate.edu to discuss research interests with ample time to develop an application for submission to NSF. Applications are due at NSF in early November. For NSF application guidelines click here.

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