Rapid transcriptome responses of maize (Zea mays) to UV-B in irradiated and shielded tissues.
BACKGROUND
Depletion of stratospheric ozone has raised terrestrial levels of ultraviolet-B radiation (UV-B), an environmental change linked to an increased risk of skin cancer and with potentially deleterious consequences for plants. To better understand the processes of UV-B acclimation that result in altered plant morphology and physiology, we investigated gene expression in different organs of maize at several UV-B fluence rates and exposure times.


RESULTS
Microarray hybridization was used to assess UV-B responses in directly exposed maize organs and organs shielded by a plastic that absorbs UV-B. After 8 hours of high UV-B, the abundance of 347 transcripts was altered: 285 were increased significantly in at least one organ and 80 were downregulated. More transcript changes occurred in directly exposed than in shielded organs, and the levels of more transcripts were changed in adult compared to seedling tissues. The time course of transcript abundance changes indicated that the response kinetics to UV-B is very rapid, as some transcript levels were altered within 1 hour of exposure.


CONCLUSIONS
Most of the UV-B regulated genes are organ-specific. Because shielded tissues, including roots, immature ears, and leaves, displayed altered transcriptome profiles after exposure of the plant to UV-B, some signal(s) must be transmitted from irradiated to shielded tissues. These results indicate that there are integrated responses to UV-B radiation above normal levels. As the same total UV-B irradiation dose applied at three intensities elicited different transcript profiles, the transcriptome changes exhibit threshold effects rather than a reciprocal dose-effect response. Transcriptome profiling highlights possible signaling pathways and molecules for future research.
Casati
Paula
P
Department of Biological Sciences, 385 Serra Mall, Stanford University, Stanford, CA 94305-5020, USA. pcasati@stanford.edu
Walbot
Virginia
V
D000064:Acclimatization / Q000235:genetics / Q000528:radiation effects; D016000:Cluster Analysis; D003201:Computers; D004307:Dose-Response Relationship, Radiation; D020869:Gene Expression Profiling / Q000379:methods / Q000706:statistics & numerical data; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D017343:Genes, Plant / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods / Q000706:statistics & numerical data; D009928:Organ Specificity / Q000235:genetics / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D010969:Plastics / Q000528:radiation effects; D018749:RNA, Plant / Q000235:genetics / Q000528:radiation effects; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D014158:Transcription, Genetic / Q000235:genetics / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects*; D003313:Zea mays / Q000235:genetics* / Q000528:radiation effects*
D010969:Plastics; D018749:RNA, Plant; D006861:Hydrogen Peroxide