Poster: Global change

Abs # 29: How high altitude maize landraces respond to ultraviolet radiation- Investigation of different mechanisms involved in UV-B acclimation.

Presenter:	Casati, Paula , pcasati@stanford.edu
Authors	Casati, Paula  (A)   Walbot, Virginia  (A)
Affiliations:	(A): Stanford University

UV-B is a natural component of sunlight, and levels of UV-B reaching the earth are increasing because of depletion of the stratospheric ozone layer. The fluence rate of UV-B in sunlight varies significantly with altitude. Consequently, analysis of maize normally grown above 2000 m, should provide insight into acclimations and adaptations from natural selection at high UV-B fluence; these lines may define the processes that confer UV-B tolerance. We studied UV-B responses in five high altitude landraces of maize: Confite Puneņo, Mishca, lines Conico, Arrocillo Amarillo, and Cacahuacintle. We tested cellular functions that are known to be affected by UV-B to compare the responses in these lines with a b, pl W23 line lacking anthocyanins. We previously found this line to be very sensitive to UV-B. UV-B induced DNA damage accumulate in the lines, but independently of the altitude were they usually grow. In terms of sunscreens, however, the high altitude landraces have high levels of two UV-B inducible flavonoids in leaves, which were identified as maysin and rhamnosylioorientin. These flavonoids are detected at very low levels in near-isogenic W23 lines, varying in B and Pl transcription factor expression. We also conducted transcriptome analysis to compare UV-B responses in the high altitude lines to the responses in W23 lines. Microarray hybridization experiments were done with landrace samples that were field-grown next to b, pl W23. We used three regimes: sunlight, no UV-B, and supplemental UV-B equal to 4X current fluence rate. From the transcriptome profiling and other attributes measured, it appears that maize plants may have independently evolved various pathways that can confer better tolerance to increased levels of UV-B present in their natural environments.