Vol 70, No 6 (2023)

Current concepts are reviewed concerning the structure, regulatory mechanisms, and the functional role of nonspecific permeability pore (also referred to as mitochondrial permeability transition pore, mPTP) located in the inner membrane of animal and plant mitochondria. Some features characterizing the functioning of mPTP in plant mitochondria and its regulation under the influence of Ca2+ and reactive oxygen species are presented. Evidence available in the literature indicates that plant mitochondria are involved in programmed cell death, and this function is due to mPTP induction among other causes. Directions for further studies of mPTP in plant mitochondria are outlined.

The formation and functioning of the photosynthetic apparatus (PSA) is under the general control of the plant organism and constantly changing environmental conditions. The authors studied age-related and adaptive changes in the pigment complex, spectral properties, and the state of photosystem II (PSII) leaves of partial shoots of a summer-winter-green herbaceous perennial Ajuga reptans L. (bugle) in connection with overwintering. Rosette leaves of a new generation appearing in May–June quickly accumulated photosynthetic pigments and formed PSA with a maximal quantum efficiency of PSII (Fv/Fm) and actual quantum yield of PSII (ФPSII). In autumn (September–October), the content of chlorophylls was 10 mg/g dry weight, the value of Fv/Fm was 0.8 rel. units, and the level of ФPSII at PAR 130 µmol quanta/(m2 s) was approximately 0.7 rel. units. Overwintered leaves contained half as much photosynthetic pigments, accumulated a significant amount of anthocyanins, and were characterized by low photochemical activity and a high level of de-epoxidation of pigments of the violaxanthin cycle. With the resumption of active vegetation of plants (May), a partial restoration of the pigment pool and the repair of PSA of overwintered leaves were noted, as evidenced by an increase in the quantum yield PSII. The completion of the leaf life cycle was accompanied by a decrease in ФPSII up to 0.5 rel. units and a sharp increase in the thermal dissipation of absorbed excitation energy (NPQ) to 0.9 rel. units. Seasonal changes of spectral properties of leaves and photochemical reflectance indices generally corresponded to the dynamics content pigments and the efficiency of the use of light in photosynthesis. The results obtained indicate a significant transformation of the structural and functional organization of PSA in the ontogeny of overwintering leaves. The genetically fixed property of winter green plants to preserve leaves is based on the ability of their PSA to restore functional activity after the shock impact of overwintering, which is facilitated by a complex of adaptive and protective mechanisms.

Carotenoids are essential participants in photosynthesis and photo protection as well as growth, development, and stress response in plants. Phytoene desaturase (PDS; EC 1.3.5.5) is an enzyme that catalyzes the first stage of desaturation of 15-cis-phytoene (a precursor to all carotenoids). In this work, we examined for the first time the effect of PDS knockout in the genome of Nicotiana tabacum L. using the CRISPR-Cas9 system on activity of downstream genes involved in biosynthesis of carotenoids. Nine transgenic lines of tobacco were obtained with a mosaic editing of gene NtPDS; three versions of indels (350^351→ins^g#, 350^351→ins^t#, and t351→del(1nt)#) in the exon II resulting in the synthesis of a shortened non-functional version of the protein. The lines were characterized by spotted, green-white pigmentation of the leaves, altered flowering time and morphology as well as a reduced content of carotenoids and chlorophylls in the leaf tissue. A rise in the level of transcripts of phytoene synthase gene NtPSY2 was shown in late-flowering lines as compared to control material. Edited line L29 with the latest flowering showed a considerable increase in the level of transcripts of downstream structural genes of carotenogenesis. A reduction in the carotenoid content in the leaves with mosaic editing was accompanied by a decrease in the level of expression of MADS-box gene NtSEP1, the product of which presumably participates in regulation of transcription of the carotenoid biosynthesis genes. The obtained results may be used for further studies of regulation of biosynthesis of carotenoids and apocarotenoids in Solanaceae.

Microgreens of four species of the family Brassicaceae (broccoli, mizuna, radish, and arugula) were grown under 16- and/or 24-h photoperiod conditions. In the first series of experiments, the daily light integral (DLI) was different (15.6 and 23.3 mol m–2 day–1 at PAR 270 µmol m–2 s–1), while it was the same (15.6 mol m–2 day–1 at PAR 270 µmol m–2 s–1 and 180 µmol m–2 s–1) in the second. In the third series of experiments, continuous lighting was used only in the last three days before harvesting. The results obtained showed that broccoli, mizuna, radish, and arugula plants in the early phases of growth are resistant to continuous lighting and do not show typical signs of leaf photodamage. In all three series of experiments, microgreens of all four species grown under 24-h photoperiod had a higher yield and nutritional value (higher content of substances with antioxidant properties—anthocyanins, flavonoids, carotenoids, and proline—as well as increased activity of antioxidant enzymes) and a lower content of nitrates compared to plants grown under 16-h photoperiod. It was concluded that it is possible through the use of continuous lighting without increasing energy costs (while maintaining the DLI) to increase the yield and nutritional value of the studied species of microgreens and reduce their nitrate content compared to the standard 16-h photoperiod. In addition, an increase in nutritional value and a decrease in nitrate content is also possible with the use of continuous lighting (as an agricultural practice) for several days immediately before harvesting.

На проростках морозостойкого сорта озимой пшеницы (Triticum aestivum L.) изучали изменения ультраструктурной организации клеток мезофилла, происходящие в процессе низкотемпературной адаптации (4°С, 7 сут). Установлено, что под влиянием низкой закаливающей температуры клетки листьев пшеницы увеличивались в размерах, при этом возрастала площадь цитоплазмы, в то время как размеры вакуоли уменьшались. Электронная плотность цитоплазмы визуально увеличивалась, в ней появлялись многочисленные везикулы. Кроме того, увеличивались размеры хлоропластов, а также количество хлоропластов, митохондрий и пероксисом на единицу площади среза клетки. Скопления митохондрий и пероксисом в виде цепочек были отмечены около хлоропластов в клетках закаленных проростков, а сами митохондрии изменяли свою форму с округлой на вытянутую или гантелевидную. Низкая температура также влияла на форму хлоропластов, которые из линзовидных становились более округлыми, в них обнаруживались выросты (стромулы). Значительные изменения под влиянием низкой температуры происходили в ультраструктуре хлоропластов: увеличивалось количество и размеры пластогбул, полностью исчезали крахмальные включения, снижались количество гран, среднее число тилакоидов в гране, высота и площадь граны, плотность фотосинтетических мембран в хлоропласте коэффициент его гранальности (отношение длины мембран тилакоидов в гранах к длине мембран стромальных тилакоидов). При этом в процессе низкотемпературного закаливания формировалась повышенная морозоустойчивость пшеницы, которую анализировали по выживаемости проростков и выходу электролитов из тканей листа после тестирующего промораживания. Показана взаимосвязь обнаруженных структурных трансформаций в клетках листьев пшеницы с функциональными и физиолого-биохимическими изменениями, происходящими у холодостойких растений в процессе низкотемпературной адаптации. Предполагается, что наблюдаемая ультраструктурная реорганизация клеток является одним из важных компонентов в сложной программе адаптации, а также звеном, необходимым для формирования повышенной устойчивости озимых злаков к низкой температуре.

The effect of heavy metals cadmium, lead, and nickel on the growth and physiological state of raphidophyte algae Heterosigma akashiwo MBRU_HAK-SR11 (Y. Hada) Y. Hada ex Y. Hara, M. Chihara during 7 days of experiments has been assessed. It was found that cadmium and nickel at concentrations of 10 and 20 µg/L stimulated H. akashiwo growth, while lead inhibited it at these concentrations. Chlorophyll a and carotenoids content increased with the addition of 10 μg/L of cadmium and 20 μg/L of nickel, and the content of carotenoids was higher than that in the control with the addition of 20 μg/L of cadmium. With the introduction of lead, an increase in the level of chlorophyll a and a decrease in the content of carotenoids were observed. The content of ROS increased with the introduction of cadmium and lead and decreased with the introduction of nickel. Cadmium had an effect on the production of neutral lipids: their content increased and decreased by the end of the experiment. Nickel stimulated the accumulation of neutral lipids H. akashiwo, while lead had no effect on their content. Metals had the least effect on forward and side light scattering and fluorescence of chlorophyll a. The absence of pronounced changes in direct and lateral light scattering indirectly indicates that the algae cells did not change morphologically under toxic exposure. Thus, cadmium, lead, and nickel at concentrations of 10–20 µg/L changed physiological processes in algae.

The photosynthetic characteristics of linden leaves (Tilia cordata L.) and birches (Betula verrukosa L.) growing near the city highways of Moscow (MKAD, Moscow Ring Road) by simultaneously recording the induction curves of chlorophyll fluorescence and the redox state of the PSI pigment–P700. In trees near highways, deterioration of electron transport at the level of plastoquinones (δRo) and decrease of P700+ reduction was revealed, despite the rather high rates of photosynthetic efficiency (FV/FM). In birch leaves growing along the Moscow Ring Road, a decrease in the outflow of electrons from PSI and a decrease in the intensity of delayed fluorescence at 30 ms and 1 s, associated with a decrease in the electrical and chemical components of the electrochemical proton gradient on photosynthetic membranes, were revealed. In plants near highways, an increase in the degree of photoinhibition and a slowdown in the reactions of restoring photosynthetic activity in the dark after the cessation of photooxidative stress were noted, which confirms the probable effect of unfavorable urban conditions on the biosynthesis of proteins in PSII reaction centers. The following fluorescence parameters are proposed as indicators of the state of trees in an urban environment: total performance index (PItotal) and the quantum yield of reduction of electron acceptors on the acceptor side of PSI (φRo).