Zea mays Transcriptome or Gene expression. Zea mays

Periods of soil water deficit could occur at any time during the crop season, but maize is particularly sensitive to water stress around flowering time. At this time the stress usually causes remarkable yield loss. Heading time, which is just before tassel flowering, is one of the most important stages that maize productivity would be affected severely if plants encounter water stress. The whole-genomic gene expression changes of maize plants in response to water deficit stress at this stage have not been studied. The present work utilized an Arizona Maize Oligonucleotide Array Version 1.9，which was consisted of A and B slides carrying with a total of 57,452 maize 70-mer oligonucleotides, was used to monitor gene expression profile changes in maize leaves subjected to 1 day and 7 days water-deficit stress respectively at the heading stage. Keywords: stress response Overall design: Maize (Zea mays L.) inbred line DH4866 was used in this study. Plants grew in flowerpots containing field soil under natural conditions. When the tassel spread out of the uppermost leaf, some plants were treated with drought stress for 7 days, and others were left under normal-watered conditions as control. In the period of the stress, the middle part of the top fully expanded leaves of the plants under water stress treatment and the control were taken to measure the leaf osmotic potential at different times by the Fiske® Micro-Osmometer (FISKE® ASSOCIATES, USA). And the stressed plants were watered every day to maintain a similar water-deficiency state by adjusting water supply, according to the osmotic potential of the fully expended leaf of the plants measured at 8:00 am each day. During the stress, the leaf osmotic potential of the stressed plants was hold to -0.4 to -0.5 Mpa, while the osmotic potential was -0.2 to -0.25 Mpa in the leaves of the control plants. And there were visible signs of water deficiency such as leaf rolling during the daytime, though at night the rolled leaves spread out. Maize plants were stress-treated at the beginning of heading stage. After 7 days of water deficiency by withholding water, the plants began to enter the flowering stage. The maize flag leaves were harvested after 24h (1d) and 168h （7d） of stress treatment, frozen in liquid nitrogen immediately and stored at -80℃ for further analysis. Unstressed plants as controls were harvested at the same time as the stressed plants. One sample consisted of the leaves from three independent plants under the same condition. Total RNA was isolated as McCarty (1986) described from the frozen samples. For each sample, 100ug of total RNA was transcribed into cDNA and fluorescently labeled with Cy3 and Cy5 dyes using the SuperScript indirect cDNA labeling system (INVITROGEN, USA) according to the manufacturer’s instructions. The Cy3 and Cy5 labels were swapped between sample and control cDNA to minimize any possible impact of inequalities in DNA incorporation and photobleaching of the fluorescent dyes. Hybridizations were performed according to the protocols at the website of the Maize Oligonucleotide Array Project. Two technical replicates (dye-swap experiments) for each biological sample from two independent treatments were performed.