College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Acclimation and Compensating Metabolite Responses to UV-B Radiation in Natural and Transgenic Populus spp. Defective in Lignin Biosynthesis(MDPI, 2022-08-20) Wong, Tiffany M.; Sullivan, Joe H.; Eisenstein, EdwardPlants have evolved to protect leaf mesophyll tissue from damage caused by UV-B radiation by producing an array of UV-absorbing secondary metabolites. Flavonoids (phenolic glycosides) and sinapate esters (hydroxycinnamates) have been implicated as UV-B protective compounds because of the accumulation in the leaf epidermis and the strong absorption in the wavelengths corresponding to UV. Environmental adaptations by plants also generate a suite of responses for protection against damage caused by UV-B radiation, with plants from high elevations or low latitudes generally displaying greater adaptation or tolerance to UV-B radiation. In an effort to explore the relationships between plant lignin levels and composition, the origin of growth elevation, and the hierarchical synthesis of UV-screening compounds, a collection of natural variants as well as transgenic Populus spp. were examined for sensitivity or acclimation to UV-B radiation under greenhouse and laboratory conditions. Noninvasive, ecophysiological measurements using epidermal transmittance and chlorophyll fluorescence as well as metabolite measurements using UPLC-MS generally revealed that the synthesis of anthocyanins, flavonoids, and lignin precursors are increased in Populus upon moderate to high UV-B treatment. However, poplar plants with genetic modifications that affect lignin biosynthesis, or natural variants with altered lignin levels and compositions, displayed complex changes in phenylpropanoid metabolites. A balance between elevated metabolic precursors to protective phenylpropanoids and increased biosynthesis of these anthocyanins, flavonoids, and lignin is proposed to play a role in the acclimation of Populus to UV-B radiation and may provide a useful tool in engineering plants as improved bioenergy feedstocks.Item Silicon modulates multi-layered defense against powdery mildew in Arabidopsis(Springer Nature, 2020-03-27) Wang, Lili; Dong, Min; Zhang, Qiong; Wu, Ying; Hu, Liang; Parson, James F.; Eisenstein, Edward; Du, Xiangge; Xiao, ShunyuanSilicon (Si) has been widely employed in agriculture to enhance resistance against pathogens in many crop plants. However, the underlying molecular mechanisms of Si-mediated resistance remain elusive. In this study, the Arabidopsis-powdery mildew pathosystem was employed to investigate possible defense mechanisms of Si-mediated resistance. Because Arabidopsis lacks efficient Si transporters and thus is a low Si-accumulator, two heterologous Si influx transporters (from barley and muskmelon) were individually expressed in wild-type Arabidopsis Col-0 and a panel of mutants defective in different immune signaling pathways. Results from infection tests showed that while very low leaf Si content slightly induced salicylic acid (SA)-dependent resistance, high Si promoted PAD4-dependent but largely EDS1- and SA-independent resistance against the adapted powdery mildew isolate Golovinomyces cichoracearum UCSC1. Intriguingly, our results also showed that high Si could largely reboot non-host resistance in an immune-compromised eds1/pad4/sid2 triple mutant background against a non-adapted powdery mildew isolate G. cichoracearum UMSG1. Taken together, our results suggest that assimilated Si modulates distinct, multi-layered defense mechanisms to enhance plant resistance against adapted and no-adapted powdery mildew pathogens, possibly via synergistic interaction with defense-induced callose.