Quantitative Trait Loci Mapping of Reproductive Traits Involved in Heat Stress Responses in Arabidopsis : Implications for Global Climate Change and Plant Reproduction Lazar Pavlovic, Greta Chiu, Jeffrey Harsant and Tammy L. Sage Department of Ecology & Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S3B2 Canada
INTRODUCTION Reproductive development in plants vulnerable to climate change because of increased frequency of heat, heat drought and salinity. salinity Global food security at risk because reproduction in many crop species currently occurs within a few degrees of temperature threshold for reproductive failure. High temperatures and other abiotic stresses due to climate change also likely to have major impacts on plant reproduction in natural ecosystems. Identification of genes that regulate reproductive tissue development during high temperature stress is key in allowing researchers to understand impact of high temperatures on plant reproduction and improve heat tolerance of plant species in natural and agricultural g ecosystems. y Primary focus of this work: understand genetic basis of heat-induced reproductive failure in Arabidopsis thaliana Ler x Cvi recombinant inbred lines (RIL s) using Quantitative Trait Loci (QTL) analysis. analysis
Viable Seed METHODS 1mm Growth Conditions: Six plants/line grown at 24/18 1mm 1 C (day/night), 16 hr photoperiod at ~360 µmol m-2s-1 of light. Aborted Seed 0.67X At initiation of reproductive meristem, three plants/line placed into each of two treatments: 4.5X Normal temperature (NT) 24/18 2.5X High (HT) 32/18 Hi h ttemperature t 1 C. 1 C. C Sampling: Ovule/seed number determined, along with carpel/silique (Image J, NSF, Version 1.42Q). Analysis: 9 reproductive traits among 2 stages of development: Stage 13 (Carpel) Non Aborted Ovules Non-Aborted Total Initiated Ovules % Abortion Ovary Length (mm) Stage 18 (Silique) Length (mm) Viable Seeds Total Initiated Ovules % Abortion Aborted Ovule Position Ovule initiation and seed abortion QTL were identified using Windows QTL Cartographer, which assumes large variation in measured variables.
RESULTS QTL mapping for ovule initiation and seed abortion QTL* in the Ler x Cvi RIL A thaliana. thaliana population of A. HT reduction in mean values of measured traits relative to NT in most lines. Large variation among lines in each of the measured traits at NT and HT large genetic potential for the traits of interest. QTL analysis lines att NT regions on Chr. l i off 65 li i Ch 1, 2 and 3 with statistically significant putative QTL containing 1 cell division gene (KRP7), loci that contribute to the phenotypic variation observed at di ttraits, it and d fl h l corresponding florall morphology genes that determine ovary/silique length and ovule/seed number. Analysis of 21 lines at HT different regions on Chr. 3, 4 and 5 with statistically significant QTL that contain different floral morphology genes, 3 HSP genes and loci contributing to the variation observed. * QTL ranges determined using the standard interval, 99% CI. 2LOD support
CONCLUSIONS Shift in genomic regions with putative QTL a potential QTL x E (Engelmann and Purugganan 2006). Acknowledgements This research was supported by the Discovery grant from the Natural Sciences Overlap between putative QTL for stage 18 % abortion and KRP7 cell division gene and Engineering Research Council of Canada (NSERC) to TLS and the Centre for at NT KRP7 may be involved in regulating % abortion. Global Change Science International Summer Internship Programme to LP. Overlap between 3 putative QTL for 6 reproductive traits and 3 HSP genes at HT Literature Cited HSP genes may regulate these reproductive traits. Engelmann, K. and Purugganan, M. (2006) The molecular evolutionary ecology of plant development: flowering time in Arabidopsis Advances in Botanical Research. p thaliana. cell-cycling/division Changes in cell cycling/division at key developmental stages 44: 507-526. smaller siliques with fewer viable seeds and/or impacted pollen tube growth. Lukens, L., Zou, F., Lydiate, D., negatively Parkin, I. and Osborn T. (2003) Comparison of a Brassica oleracea genetic map with the genome of Arabidopsis thaliana. Genetics. 164: 359-372. pp g of identified QTL Q using g near-isogenic g ) Future studies: fine mapping lines ((NIL s). The Arabidopsis Information Resource (TAIR). 21 August 2009 < http://www.arabidopsis.org/ > gene knockout experiments to pinpoint precise gene(s) regulating plant responses to HT stress. boost heat tolerance of plant species via selective breeding and other methods of genetic modification.