Studies on the genetic basis for thermotolerance in Arabidopsis thaliana

Vast tracts of land are available for arable food production but much of this is located in hot, arid regions. For crops to thrive in these conditions they will need to show improved drought tolerance and also improved thermotolerance as low water availability reduces transpiration resulting in increased leaf temperatures. Identification of traits and genes involved in drought tolerance has been one of the major areas of plant research over the last decade, but thermotolerance has received little attention. In this study two approaches were used to identify the genetic basis for improved thermotolerance in the model plant Arabisopsis thaliana. In one set of experiments a gain-of-function heat stress screen (44 oC for 3 hours) was performed on a collection of Activation Tagged lines where individual plants were engineered to transcriptionally activate random sequences in the Arabidopsis genome. Preliminary experiments confirmed prior exposure to 37 oC for 1-3 hours acclimates Arabidopsis so that it survives better a subsequent heat stress event. A total of ~14,600 lines were screened and three mutants were isolated; secondary screens confirmed their improved thermotolerance phenotype, but in subsequent generations one of the lines developed a hypersensitive phenotype, another reverted to wild type, whilst the third retained its thermotolererant phenotype. This loss-of-phenotype through generations was attributed to gene silencing events which are not uncommon in dominant mutants. Further experiments on these three lines are now required to identify the loci of the disrupted gene(s) in each of these lines. In the other set of experiments transgenic lines carrying a construct designed to constitutively express a MYB transcription factor were characterized. This MYB has been shown to confer salinity tolerance in Arabidopsis, and transcript profiling using cDNA microarrays had identified several sequences may be under the control of this MYB. Quantitative PCR (QRT-PCR) demonstrated that compared with wild type MYB expression in the transgenic lines was over 500 times greater, and that transcript for a small heat shock protein AtHSP17.6, is 17 times more abundant. These transgenic lines were shown to have an improved thermotolerance. Treatment of wild type plants with 5 x 10-4 M ABA increased the expression of this MYB seven-fold, suggesting this transcription factor forms part of the ABA-dependent pathway for the activation of abiotic stress responses in Arabidopsis.

Level dc:type.qualificationlevel

MSc(R)

Grantor dc:publisher.institution

University of Glasgow

Year dc:date.issued

2009

Author dc:creator

• Nurcahyanti, Agustina

• QK Botany
• S Agriculture (General)

Language dc:language

en