In light of recent climate change, with its rising temperatures and precipitation changes, we are facing the need to increase the valuable crop’s tolerance against unfavorable environmental conditions. Emmer wheat is a cereal crop with high nutritional value. We investigated the possibility of improving the stress tolerance of emmer wheat by activating the synthesis of the stress hormone jasmonate by overexpressing two genes of the jasmonate biosynthetic pathway from Arabidopsis thaliana, ALLENE OXIDE SYNTHASE (AtAOS) and OXOPHYTODIENOATE REDUCTASE 3 (AtOPR3). Analyses of jasmonates in intact and mechanically wounded leaves of non-transgenic and transgenic plants showed that the overexpression of each of the two genes resulted in increased wounding-induced levels of jasmonic acid and jasmonate-isoleucine. Against all expectations, the overexpression of AtAOS, encoding a chloroplast-localized enzyme, does not lead to an increased level of the chloroplast-formed 12-oxo-phytodienoic acid (OPDA), suggesting an effective conversion of OPDA to downstream products in wounded emmer wheat leaves. Transgenic plants overexpressing AtAOS or AtOPR3 with increased jasmonate levels show a similar phenotype, manifested by shortening of the first and second leaves and elongation of the fourth leaf, as well as increased tolerance to osmotic stress induced by the presence of the polyethylene glycol (PEG) 6000.

12-Oxophytodienoate reductase is the enzyme involved in the biosynthesis of phytohormone jasmonates, which are considered to be the major regulators of plant tolerance to biotic challenges, especially necrotrophic pathogens. However, we observe compromised tolerance to the necrotrophic fungal pathogen Botrytis cinerea in transgenic hexaploid bread wheat and tetraploid emmer wheat plants overexpressing 12-OXOPHYTODIENOATE REDUCTASE-3 gene from Arabidopsis thaliana, while in Arabidopsis plants themselves, endogenously produced and exogenously applied jasmonates exert a strong protective effect against B. cinerea. Exogenous application of methyl jasmonate on hexaploid and tetraploid wheat leaves suppresses tolerance to B. cinerea and induces the formation of chlorotic damages. Exogenous treatment with methyl jasmonate in concentrations of 100 µM and higher causes leaf yellowing even in the absence of the pathogen, in agreement with findings on the role of jasmonates in the regulation of leaf senescence. Thereby, the present study demonstrates the negative role of the jasmonate system in hexaploid and tetraploid wheat tolerance to B. cinerea and reveals previously unknown jasmonate-mediated responses.

Photosynthesis is a vital process for seed productivity. It occurs in the leaves and provides developing seeds with the necessary nutrients. Moreover, many crops require photochemical reactions inside the seeds for proper development. The present study aimed to investigate Pisum sativum L. seeds at the middle stage of maturation, which is characterized by the active synthesis of nutrient reserves. Embryonic photosynthesis represents a crucial process to produce cells’ NADP(H) and ATP, which are necessary to convert sucrose into reserve biopolymers. However, it remains unclear how the pea embryo, covered by a coat and pericarp, receives sufficient light to provide energy for photochemical reactions. Recent studies have demonstrated that the photosynthetically active radiation reaching the developing pea embryo has a high proportion of green light. In addition, green light can be utilized in foliar photosynthesis by plants cultivated in shaded conditions. Here, we addressed the role of green light in seed development. Pea plants were cultivated under red and blue (RB) LEDs or red, green, and blue (RGB) LEDs. A Chl a fluorescence transient based on OJIP kinetics was detected at the periphery of the cotyledons isolated from developing seeds. Our findings showed that the addition of green light resulted in an increase in photochemical activity. Furthermore, the mature seeds that developed in the RGB module had a significantly higher weight and more storage proteins. Using a metabolomics approach, we also detected significant differences in the levels of organic acids, carbohydrates, nucleotide monophosphates, and nitrogenous substances between the RB and RGB conditions. Under RGB light, the cotyledons contained more ornithine, tryptophan, arginine, and aspartic acid. These changes indicate an impact of green light on the ornithine–urea cycle and polyamine biosynthesis. These results allow for a deeper understanding of the photochemical processes in embryos of developing seeds grown under a low light intensity. The photosynthetic system in the embryo cell adapts to the shade conditions by using green light.

This content was removed at the authors' request because of conflict with journal policy.