Date of Graduation

8-2013

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Vibha Srivastava

Committee Member

Craig S. Rothrock

Second Committee Member

Kristofor Brye

Third Committee Member

Derrick M. Oosterhuis

Keywords

Biological sciences; Arabidopsis; Chlorophyll fluorescence; Cotton; Gene expression; Gossypium hirsutum; Heat tolerance; Membrane leakage

Abstract

ABSTRACT

Heat stress causes major losses to cotton seed and lint yield. Introduction of heat stress tolerance to Arkansas cotton varieties is highly desirable. However, very little is known about the molecular basis of heat stress tolerance in cotton. The present study attempted to identify heat stress tolerance genes in two heat-tolerant cotton cultivars, VH260 and MNH456, originating from Pakistan. Towards this, the expression profile of the cotton orthologs of seven Arabidopsis heat stress tolerance genes was studied in these two cultivars, and compared with the two heat-susceptible cotton cultivars, ST213 and ST4288, originating from Mississippi Delta region. In addition, physiological parameters such as membrane leakage and chlorophyll fluorescence in the two set of varieties were studied to analyze the correlation between gene expression and physiological data. The gene expression data indicated that both heat-tolerant cultivars highly express heat-shock proteins and heat-shock transcription factors after heat treatment whereas heat-susceptible cultivars show a lower expression. Similarly, Ascorbate Peroxidase I and Annexin 8, the two general stress proteins are also highly induced in at least one of the heat tolerant cultivars in response to heat treatment. No obvious differences were found in photochemical efficiency of PSII in the four lines. However, heat susceptible cultivars show greater membrane leakage after heat treatment as compared to the heat tolerant lines. This work suggests that early induction of heat stress tolerance genes such as heat shock proteins and heat shock factors play an important role in conferring heat stress on cotton varieties, VH260 and MNH456.

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