Phenylalanine Is Required to Promote Specific Developmental Responses and Prevents Cellular Damage in Response to Ultraviolet Light in Soybean (Glycine max) during the Seed-to-Seedling Transition

Abstract

UV-radiation elicits a suite of developmental (photomorphogenic) and protective responses in plants, but responses early post-germination have received little attention, particularly in intensively bred plants of economic importance. We examined germination, hypocotyl elongation, leaf pubescence and subcellular responses of germinating and/or etiolated soybean (Glycine max (L.) Merr.) seedlings in response to treatment with discrete wavelengths of UV-A or UV-B radiation. We demonstrate differential responses of germinating/young soybean seedlings to a range of UV wavelengths that indicate unique signal transduction mechanisms regulate UV-initiated responses. We have investigated how phenylalanine, a key substrate in the phenylpropanoid pathway, may be involved in these responses. Pubescence may be a key location for phenylalanine-derived protective compounds, as UV-B irradiation increased pubescence and accumulation of UV-absorbing compounds within primary leaf pubescence, visualized by microscopy and absorbance spectra. Mass spectrometry analysis of pubescence indicated that sinapic esters accumulate in the UV-irradiated hairs compared to unirradiated primary leaf tissue. Deleterious effects of some UV-B wavelengths on germination and seedling responses were reduced or entirely prevented by inclusion of phenylalanine in the growth media. Key effects of phenylalanine were not duplicated by tyrosine or tryptophan or sucrose, nor is the specificity of response due to the absorbance of phenylalanine itself. These results suggest that in the seed-to-seedling transition, phenylalanine may be a limiting factor in the development of initial mechanisms of UV protection in the developing leaf.

Transcriptional Activation of Anthocyanin Biosynthesis in Developing Fruit of Blueberries (Vaccinium corymbosum L.) by Preharvest and Postharvest UV Irradiation

“…Many studies on the effects of UV treatment in horticultural crops were conducted in postharvest fruit and focus on inhibition of storage rot, increased antioxidant capacity, and contents of health-promoting compounds. However, only limited research − was conducted on the application of UV radiation to field plants, and this research mainly focused on vegetative plant organs (such as leaves) rather than on reproductive organs (flower and fruit). Plants exhibit inter- and intraspecific differences in UV tolerance, , which can vary with the phenological stage of development.…”

New Insights Into Lignification via Network and Multi-Omics Analyses of Arogenate Dehydratase Knock-Out Mutants in Arabidopsis thaliana

“…It may be an interesting and informative exercise to further explore correlative enzyme abundances to other phenylpropanoids that may play a more central role in leaf tissue function. For example, those associated with UV protection (e.g., flavonoids and sinapate esters) ( Stapleton and Walbot, 1994 ; Landry et al, 1995 ; Mazza et al, 2000 ; Clé et al, 2008 ; Sullivan et al, 2014 ), in order to tease out specific post-transcriptional biosynthesis regulation of formation of these other phenylpropanoids.…”

Chromatin states responsible for the regulation of differentially expressed genes under 60Co~γ ray radiation in rice

“…However, many up-regulated biological processes, such as biosynthetic, metabolic and cellular processes, may help to prevent against IR-induced cell damage. The involvement of phenylalanine in cellular damage has been found in soybean in response to ultraviolet light [ 36 ]. As a precursor for the synthesis of phyto-hormones, such as abscisic acid (ABA) and other chemicals, pyruvic acid plays important roles in mediating the function of chloroplast in plant stress responses, such as those in response to salt [ 37 ].Thus, IR-induced differential gene expression causes two-sided effects: negative and positive regulation of cell development and plant growth.…”