Drought response in the spikes of barley: gene expression in the lemma, palea, awn, and seed
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The photosynthetic organs of the barley spike (lemma, palea, and awn) are considered resistant to drought. However, there is little information about gene expression in the spike organs under drought conditions. We compared response of the transcriptome of the lemma, palea, awn, and seed to drought stress using the Barley1 Genome Array. Barley plants were exposed to drought treatment for 4 days at the grain-filling stage by withholding water. At the end of the stress, relative water content of the lemma, palea, and awn dropped from 85% to 60%. Nevertheless, the water content of the seed only decreased from 89% to 81%. Transcript abundance followed the water status of the spike organs; the awn had more drought-regulated genes followed by lemma and palea, and the seed showed very little change in gene expression. Despite expressing more drought-associated genes, many genes for amino acid, amino acid derivative, and carbohydrate metabolism, as well as for photosynthesis, respiration, and stress response, were down-regulated in the awn compared with the lemma, palea, and seed. This suggests that the lemma and the palea are more resistant to drought stress compared with the awn.
KeywordsAwn Drought Lemma Palea Seed Transcriptome
We thank Diveena Vijeyandran, Aaron Walck, Ng Eng Hwa, Emily Jackson, and Justin Wilkins for their help on sample collection and RNA extraction and Matthew Moscou for initial analysis of the data set. We are grateful to Billie Hemmer and Stephanie Witt for assistance in growing plants. We thank Dr. Tesfaye Mersha for his advice on statistical analysis. This work was supported by the Board of Regents of the State of Iowa and the Office of Sponsored Programs, the Graduate College, the College of Natural Sciences and the Department of Biology of the University of Northern Iowa, Cedar Falls, Iowa. We thank Dr. Ronald W. Skadsen for his valuable comments.
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