10.1021/pr901113z.s002 Stephanie Kaspar Stephanie Kaspar Andrea Matros Andrea Matros Hans-Peter Mock Hans-Peter Mock Proteome and Flavonoid Analysis Reveals Distinct Responses of Epidermal Tissue and Whole Leaves upon UV−B Radiation of Barley (<i>Hordeum vulgare</i> L.) Seedlings American Chemical Society 2010 barley seedling leaf epidermis Whole Leaves flavonoid molecule Flavonoid Analysis gel electrophoresis oxidative stress metabolism proteins UV flavonoid content Flavonoid analysis Distinct Responses mesophyll tissue epidermis tissue DE Epidermal Tissue expression pattern protein expression 2010-05-07 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Proteome_and_Flavonoid_Analysis_Reveals_Distinct_Responses_of_Epidermal_Tissue_and_Whole_Leaves_upon_UV_B_Radiation_of_Barley_i_Hordeum_vulgare_i_L_Seedlings/2771722 We describe here the effect of UV−B irradiation on the proteome and flavonoid content of the barley seedling leaf epidermis and mesophyll. Flavonoid analysis was performed using UPLC-PDA/-MS. The major flavonoid molecule responding to UV−B radiation was saponarin, and this accumulated in the epidermis, but not in the mesophyll. Changes in protein expression were determined using two-dimensional gel electrophoresis (2-DE) and identified 11 responsive proteins (seven up-regulated and two down-regulated in the epidermis; and one up- and one down-regulated in the mesophyll). A label-free LC-MS/MS<sup>E</sup> approach was applied for a subset of samples consisting of epidermis tissue and was able to detect a further 15 (11 up-regulated and four down-regulated) proteins. Most of the proteins with changed expression pattern after UV−B treatment were involved in initial responses characteristic for oxidative stress. Others were primary metabolism proteins involved in the supply of precursors for secondary metabolites. A separate analysis of epidermis and mesophyll tissue is important to give a spatially resolved picture of the response to UV−B treatment. The label-free LC-MS/MS<sup>E</sup> approach is complementary to the more conventional two-dimensional gel electrophoresis, as there was no overlap between the spectra of proteins identified by the two techniques.