Alexey V. Pigolev

In this article, a distinctive feature of invasive tree boxelder ( Acer negundo ), associated with the significant presence and high photosynthetic activity of the chlorenchyma tissues in the tree branches, is highlighted. The chlorenchyma layer on the surface of the branches is maintained for several years, and photosynthetic activity can be detected directly from the surface of branches almost throughout the entire year. Phytohormone analysis of the chlorenchyma layer of A. negundo branches revealed a high content of salicylic acid, which is known to mediate broad protective functions. Laboratory analysis of the dependence of chlorophyll fluorescence parameters on light intensity showed that the effective quantum yield of photosystem II in A. negundo branch surface chlorenchyma is noticeably suppressed with increasing light intensity, and relative electron transport rate at PSII is significantly lower than in the leaf at all applied light intensities. At the same time, branch surface chlorenchyma in A. negundo is characterized by the ability to rapidly recover variable chlorophyll fluorescence after turning off the actinic light. Fast decrease of variable chlorophyll fluorescence under light and its recovery in the dark are associated with a high contribution of the high-energy state fluorescence quenching component (qE) to non-photochemical quenching in this tissue. Apparently, this mechanism of non-photochemical quenching protects the photosynthetic apparatus of the branch surface chlorenchyma from the damaging effect of excessive light.

Гранулометрическое разделение почвенного органического вещества (ОВ) на фракциидисперсного (РОМ; размер частиц 53–2000 мкм) и минерально-ассоциированного ОВ (МАОМ; менее 53 мкм) является простым и широко используемым подходом к оценке его устойчивости к микробному разложению. Важной процедурой при выполнении данного анализа является предварительная обработка почвенного образца для разрушения агрегатов и извлечения из них стабильного пула МАОМ. В связи с этим, наше исследование было нацелено на сравнительную оценку двух наиболее часто используемых подходов диспергирования почвы: химического (0,5% раствор гексаметафосфата натрия; ГМФ) и физического (ультразвуковое воздействие при 60 Дж мл–1; УЗ). В качестве объекта исследования был выбран агрочернозем тяжелосуглинистый (слой 0–10 см; n = 30), отобранный c производственных полей Самарской области. Содержание органического углерода в выбранных образцах почвы варьировало от 2,7 до 5,6%, углерода карбонатов – от 0,02 до 3,60%, значения рН – от 5,9 до 7,8, фракции ила (< 2 мкм) – от 22 до 34%, пыли (2–50 мкм) – от 51% до 65%. Минералогический состав пылевато-илистой фракции представлен кварцем, плагиоклазами, калиевыми полевыми шпатами, амфиболами, триоктаэдрические и диоктаэдрическими слюдами, карбонатами (кальцит, доломит), хлоритами и монтмориллонитом. Результаты гранулометрического фракционирования показали, что диспергирование агрочернозема ГМФ по сравнению с УЗ дает вдвое большую массу выделяемой фракции РОМ из-за недостаточного разрушения микроагрегатов размером 50–250 мкм. В результате происходит недооценка вклада стабильной фракции МАОМ в общий пул ОВ почвы в среднем на 41%. Таким образом, для агрочерноземов тяжелосуглинистых применение химического способа диспергирования для гранулометрического фракционирования ОВ оказалось менее эффективным по сравнению с физическим. Particle-size fractionation of soil organic matter (OM) into particulate (POM; particle size 53–2000 µm) and mineral-associated OM (MAOM; <53 µm) pools is a simple and widely used approach to assess OM stability against microbial degradation. Soil sample pre-treatment to break down aggregates and release the stable MAOM pool is a crucial step for this analysis. Our study was aimed at a comparative assessment of two commonly used approaches of soil pre-treatment for particle-size fractionation: chemical (0.5% hexametaphosphate solution; HMP) and physical (sonification at 60 J ml–1; US). The tested soil was silt loam Chernozem, taken from the upper 0–10 cm layer (n= 30) of agricultural lands in the Samara region. Soil organic carbon content in the soil ranged from 2.7 to 5.6%, carbonate carbon from 0.02 to 3.60%, pH values from 5.9 to 7.8, clay (< 2 μm) from 22 to 34%, and silt (2–50 μm) from 51% to 65%. The mineralogical composition of the clay-silt fraction was represented by quartz, plagioclase, potassium feldspars, amphiboles, trioctahedral and dioctahedral micas, carbonates (calcite, dolomite), chlorites and montmorillonite. The particle-size fractionation of the soil samples showed that HMF treatment resulted in twice as much POM pool release compared to US treatment due to insufficient destruction of microaggregates of 50–250 µm. This resulted in an average underestimation of the MAOM pool by 41%. Therefore, for the particle-size fractionation of OM in silt loam Chernozems, the ultra-sound pre-treatment of soil samples is preferable to the treatment with sodium hexametaphosphate solution.

Our knowledge of photosynthesis in non-foliar tissues is still limited, especially about the tolerance of photosynthetic apparatus in these tissues to unfavorable environmental factors. Here we monitored the activity of photosystem II in leaves and vine chlorenchyma in grapevine (Vitis vinifera L.) during the period of active vegetative growth. Both tissues maintained high values of effective quantum yield of photosystem II (Y(II)) over the whole period of hot sunny weather, while Y(II) values were consistently higher in vine. No significant correlation between Y(II) and environmental conditions was found, and there was no influence of phenological phases on this parameter. Laboratory measurements demonstrated a high tolerance of photosynthetic apparatus in vine chlorenchyma to high temperatures (up to 50°C). Non-photochemical quenching and the contribution of different components, including the energy-dependent component, associated with transthylakoid pH gradient and functioning of the violaxanthin cycle (q_E); quenching due to redistribution of excitation energy between the reaction centers of photosystems (q_T); and quenching induced by photoinhibition (q_I) at different light intensities were estimated. The contribution of q_I was high at all light intensities, and it increases with increasing light intensity, while the contribution of q_E and q_T was smaller and reached maximal values at low light intensities. The analysis of carotenoids showed that compared to the leaf, vine chlorenchyma is characterized by high lutein and xanthophyll content with antheraxanthin being a dominant xanthophyll, a lower violaxanthin-to-zeaxanthin ratio, but higher xanthophyll de-epoxidation index. This work contributes to our understanding of photosynthetic processes in non-foliar tissues under various environmental conditions.

This article describes the negative effects of exogenously applied and endogenously produced jasmonates in the tolerance of bread wheat ( Triticum aestivum L.) plants of the Saratovskaya-60 cultivar to excessive light conditions. While no significant effect of jasmonates on the variable chlorophyll fluorescence parameters is evident under moderate and low light conditions, the negative effect of jasmonates at high light intensities is evident on a “rapid light curve” of methyl jasmonate (MeJA)-treated plants and transgenic plants Tr-20 overexpressing 12-OXOPHYTODIENOATE REDUCTASE 3 ( AtOPR3 ), a jasmonate biosynthesis gene from Arabidopsis thaliana . The analysis of fast chlorophyll fluorescence kinetics with high-time resolution (OJIP test) confirmed the difference between Tr-20, MeJA-treated and mock treated ‘Saratovskaya-60’. Two hours of plant leaves incubation under photoinhibitory light induce clearly visible changes in OJIP kinetics, and these changes are more pronounced in MeJA-treated and Tr-20 leaves as lower values of kinetic transient points J, I, and P. Subsequent two-hour incubation under low light leads to an almost complete recovery of the OJIP kinetics in leaves of mock treated ‘Saratovskaya-60’ leaves, while only partial recovery is observed in the leaves of MeJA-treated and Tr-20 plants. The transgenic line Tr-3, which under high light conditions does not accumulate more jasmonates than non-transgenic parental line, does not differ in tolerance to photoinhibition from the non-transgenic plants, confirming that the increased level of jasmonates is necessary to compromise the tolerance to photoinhibition. Analysis of stress hormones revealed the role of jasmonates in modulating the level of abscisic acid and salicylic acid during wheat leaves adaptation to high-light conditions. The data obtained lay the foundation for further studies of complex hormonal cross-talk in wheat leaves under light stress conditions.

The photosynthetic apparatus in chlorenchyma tissues of lignified tree branches is subjected to fluctuations in environmental temperatures throughout the year. In the present study, the effective quantum yield of photosystem II (Y(II)) in chlorenchyma tissues of apple tree (Malus × domestica Borkh.) branches was monitored on a weekly basis over two years. The activity of photosystem II in these tissues during all seasons has been detected. Microscopic analysis confirmed the presence of chlorenchyma cells mainly localized under the bark during all seasons, even in old branches. Correlation analysis demonstrates that Y(II) is strongly dependent on the air temperature, with an increase in the temperature range of 0 to 10°C contributing most significantly to the Y(II) growth. At negative air temperatures, Y(II) values vary between 0 and 0.2, although in rare instances higher values have been detected. Notably, the photosynthetic potential of winter branches is retained, and incubation of branches at room temperature restores the functionality of photosystem II rapidly. A comparison of the tolerance of the photosynthetic apparatus of M. domestica branches collected at different seasons to elevated temperatures revealed that summer branches demonstrate the highest tolerance to high-temperature stress, while by winter their ability to withstand increased temperatures diminished noticeably. Overall, the results demonstrate that the photosynthetic apparatus in M. domestica branches exhibits persistent activity throughout the year, though its physiological characteristics are subject to seasonal variations.

The transformation protocol based on the dual selection approach (fluorescent protein and herbicide resistance) has been applied here to produce transgenic plants of two cereal species, emmer wheat and bread wheat, with the goal of activating the synthesis of the stress hormone jasmonates by overexpressing ALLENE OXIDE SYNTHASE from Arabidopsis thaliana (AtAOS) and bread wheat (TaAOS) and OXOPHYTODIENOATE REDUCTASE 3 from A. thaliana (AtOPR3) under the strong constitutive promoter (ZmUbi1), either individually or both genes simultaneously. The delivery of the expression cassette encoding AOS was found to affect morphogenesis in both wheat species negatively. The effect of transgene expression on the accumulation of individual jasmonates in hexaploid and tetraploid wheat was observed. Among the introduced genes, overexpression of TaAOS was the most successful in increasing stress-inducible phytohormone levels in transgenic plants, resulting in higher accumulations of JA and JA-Ile in emmer wheat and 12-OPDA in bread wheat. In general, overexpression of AOS, alone or together with AtOPR3, negatively affected leaf lamina length and grain numbers per spike in both wheat species. Double (AtAOS + AtOPR3) transgenic wheat plants were characterized by significantly reduced plant height and seed numbers, especially in emmer wheat, where several primary plants failed to produce seeds.

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.

CИСТЕМА ОЦЕНКИ МЯСНОГО СКОТА ПО ПОКАЗАТЕЛЯМ ЭФФЕКТИВНОСТИ ИСПОЛЬЗОВАНИЯ КОРМА И ЭНЕРГИИ РОСТА НА ОСНОВЕ ПРИМЕНЕНИЯ ЦИФРОВЫХ И ГЕНОМНЫХ ТЕХНОЛОГИЙ (обзор) А.А. БЕЛОУС, А.А. СЕРМЯГИН, Н.А. ЗИНОВЬЕВА

ISHS VIII International Scientific and Practical Conference on Biotechnology as an Instrument for Plant Biodiversity Conservation (Physiological, Biochemical, Embryological, Genetic and Legal Aspects) Genetic modification of jasmonate biosynthesis pathway in wheat alters plant tolerance to necrotrophic fungi