Oral Delivery of Double-Stranded RNAs and siRNAs Induces RNAi Effects in the Potato/Tomato Psyllid, Bactericerca cockerelli

The potato/tomato psyllid, Bactericerca cockerelli (B. cockerelli), and the Asian citrus psyllid, Diaphorina citri (D. citri), are very important plant pests, but they are also vectors of phloem-limited bacteria that are associated with two devastating plant diseases. B. cockerelli is the vector of Candidatus Liberibacter psyllaurous (solanacearum), which is associated with zebra chip disease of potatoes, and D. citri is the vector of Ca. Liberibacter asiaticus, which is associated with the Huanglongbing (citrus greening) disease that currently threatens the entire Florida citrus industry. Here we used EST sequence information from D. citri to identify potential targets for RNA interference in B. cockerelli. We targeted ubiquitously expressed and gut-abundant mRNAs via injection and oral acquisition of double-stranded RNAs and siRNAs and were able to induce mortality in recipient psyllids. We also showed knockdown of target mRNAs, and that oral acquisition resulted primarily in mRNA knockdown in the psyllid gut. Concurrent with gene knockdown was the accumulation of target specific ∼ 21 nucleotide siRNAs for an abundant mRNA for BC-Actin. These results showed that RNAi can be a powerful tool for gene function studies in psyllids, and give support for continued efforts for investigating RNAi approaches as possible tools for psyllid and plant disease control

Lignification in Zinnia (Zinnia elegans Jacq.) Stem Sections of Different Age: Biochemical and Molecular Genetic Traits

Lignification of the stem in zinnia provides its mechanical properties due to xylem formation, which depends on the stage of plant development and is responsible for the transport of water and minerals. The study was aimed at the lignin deposition, anatomical traits, biochemical markers of lignification, as well as the genetic regulation of this process in zinnia stem cross sections of different age during their radial growth. The anatomical traits were assessed on cross sections. The content of lignin (Cysteine-assisted sulfuric method (CASA) and the thioglycolic acid (TGA) methods), the spectrum of phenolics (by thin layer chromatography (TLC)), the total activity and the variety of class III peroxidases were determined. The expression level of genes regulating phenylpropanoids and lignin biosynthesis were assessed. We suggest that time-specific and organ-specific lignification is determined by the metabolism of phenolic compounds and depends on the expression of genes of the phenylpropanoid pathway. It was shown that in the hypocotyl, during xylem ring formation, lignification was associated with increased expression of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) genes responsible for the early stages of the phenylpropanoid pathway, and with the rise of class III peroxidases activity, including cationic isoforms. This caused increased content and diversity of phenolics in mature hypocotyl. In epicotyl, which is younger than the hypocotyl, the proportion of ferulic acid among phenolics increased, which could be considered as a marker of lignification in it. The high expression level of CAD and the activity of peroxidases, including anionic isoforms, led to accumulation of lignin. Thus, the hypocotyl and epicotyl, being characterized by different ages, differed in spectrum of phenolics, isoforms of class III peroxidases, expression of the PAL, cinnamate 4-hydroxylase (C4H), peroxidases III class (PRX), and laccase (LAC) genes, and lignin content. © 2023 by the authors.Russian Science Foundation, RSF: 22-24-00817This research was supported by Russian Science Foundation, Project No. 22-24-00817, https://rscf.ru/project/22-24-00817/ (accessed on 26 February 2023)

A dominant repressor version of the tomatoSl-ERF.B3gene confers ethylene hypersensitivity via feedback regulation of ethylene signaling and response components

Ethylene Response Factors (ERFs) are downstream components of the ethylene signal transduction pathway, although their role in ethylene-dependent developmental processes remains poorly understood. As the ethylene-inducible tomato Sl-ERF.B3 has been shown previously to display a strong binding affinity to GCC-box-containing promoters, its physiological significance was addressed here by a reverse genetics approach. However, classical up- and down-regulation strategies failed to give clear clues to its roles in planta, probably due to functional redundancy among ERF family members. Expression of a dominant repressor ERF.B3-SRDX version of Sl-ERF.B3 in the tomato resulted in pleiotropic ethylene responses and vegetative and reproductive growth phenotypes. The dominant repressor etiolated seedlings displayed partial constitutive ethylene response in the absence of ethylene and adult plants exhibited typical ethylene-related alterations such as leaf epinasty, premature flower senescence and accelerated fruit abscission. The multiple symptoms related to enhanced ethylene sensitivity correlated with the altered expression of ethylene biosynthesis and signaling genes and suggested the involvement of Sl-ERF.B3 in a feedback mechanism that regulates components of ethylene production and response. Moreover, Sl-ERF.B3 was shown to modulate the transcription of a set of ERFs and revealed the existence of a complex network interconnecting different ERF genes. Overall, the study indicated that Sl-ERF.B3 had a critical role in the regulation of multiple genes and identified a number of ERFs among its primary targets, consistent with the pleiotropic phenotypes displayed by the dominant repression lines

Copper Stress Enhances the Lignification of Axial Organs in Zinnia elegans

Zinnia elegans Jacq. is an ornamental plant, widely used in landscaping. Heavy-metal pollution in urban and rural areas is still increasing, which determines the actuality of studying plants’ reactions to pollutants. Zinnia was not sufficiently studied in this regard, so the aim of our research was to identify morphophysiological changes in this species under excess copper concentration in the soil. For this, we treated a growth substrate with 200 µM CuSO4 solution for 20 days. At the end of the treatment, several morphological, biochemical, and molecular genetic traits were evaluated: the root and the shoot size; the concentration of H2O2 and malondialdehyde (MDA), as indicators of stress; the amount of the phenolic compounds and lignin; and the level of the expression of genes, which encoded their biosynthesis. The Cu amount in the substrate and zinnia organs was quantified using atomic-absorption spectroscopy; hydrogen peroxide, MDA, and phenolic compounds were determined spectrophotometrically, while the amount of lignin was determined according to Klason. Real-time PCR was used for estimation of the gene-transcription level. Lignin in tissues was visualized by fluorescent microscopy. In experimental plants, Cu accumulation was higher in the root than in the stem. This caused an increase in stress markers and a decrease in the root and stem lengths. For the first time for zinnia, it was shown that for several genes—4-coumarate-CoA ligase (4CL), cinnamoyl alcohol dehydrogenase (CAD), and class III peroxidase (PRX)—the level of expression increased under copper treatment. The rise of the transcripts’ amount of these genes was accompanied by a thickening and lignification of the cell walls in the metaxylem vessels. Thus, the adaptation of zinnia to the excess Cu in the growth medium was associated with the metabolic changes in the phenylpropanoid pathway. As a result, the lignification increased in the root, which led to the accumulation of Cu in this organ and limited its translocation through the xylem to the stem, which provided plant growth. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 22-24-00817Funding: This research was supported by the Russian Science Foundation, project no. 22-24-00817, https://rscf.ru/project/22-24-00817/, accessed date: 17 July 2022

Recovery of growth in Zinnia elegans after copper stress

The symptoms of copper ion toxicity are well studied, but there is limited information on the mechanisms of plant recovery after stress. The paper deals with the recovery of growth in Zinnia elegans Jacq., treated with 50 and 100 µM Cu2+ for 15 days, then cultivated in normal condition for 30 days. After the recovery period the length of shoot, anatomical changes of root, hypocotyl and stem (first internode) were investigated. It was shown that the copper ions induced a decrease of plant length during stress period. After stress relief for 30 days, the length of hypocotyl and stem of Cu-treated plants increased compared to control. The diameter of root was bigger due to the increase in thickness of cortex and stele. The changes were less noticeable in shoot tissues. The diameter of hypocotyl positively correlates with the thickness of stele. Same effect of copper was observed in stem only in plants, previously treated with 100 µM. The diameter of cortex and metaxylem cells increased in all analyzed organs. No significant differences were found in cell wall thickness of metaxylem cells. The recovery of Z. elegans growth after cooper treatment occurred due to the expansion of cortex and metaxylem cells. © 2021 Author(s).Department of Science and Technology, Ministry of Science and Technology, India, डीएसटी, (ʋ 19-516-45006)Russian Foundation for Basic Research, РФФИGovernment Council on Grants, Russian FederationThe work was funded by RFBR and DST (research project ʋ 19-516-45006) and the Government of the Russian Federation, Act 211 (contract ʋ 02.A03.21.0006)

Экспрессия генов метаболизма фенолов и лигнина в Zinnia elegans в условиях засоления

Salinization is a common type of agricultural land degradation. It causes inhibition of plant growth and productivity. Previous research into mechanisms of plant resistance to salinity and other stressors has shown that one of nonspecific responses is cell wall lignification which limits translocation of water and ions in the tissues and the whole plant. The current study aims to investigate the responses of Zinnia elegans Jacq. grown under regular soil irrigation with 50 mM NaCl. Plant growth parameters and biochemical characteristics, such as the level of hydrogen peroxide and malondialdehyde (MDA), and phenolics and lignin content, were determined. The level of expression of genes encoding the biosynthesis of phenolic compounds and lignin was evaluated by the relative number of transcripts. Application of 50 mM NaCl to soil decreased plant growth and induced lipid peroxidation in stem tissues, despite an increase in the concentration of phenolic compounds. It means that the antioxidant potential of produced phenolics might be insufficient for plant protection. The amount of lignin in stem tissues increased mainly due to Klason lignin which is known to limit cell elongation. The concentration of phenolic compounds correlated with the expression of PAL, C4H and 4CL genes involved in their biosynthesis; and the amount of lignin correlated with the expression level of CCR, CAD, PRX, and LAC genesЗасоление – распространенный вид нарушения сельскохозяйственных земель. Оно вызывает угнетение роста и продуктивности растений. Изучение механизмов устойчивости растений к засолению показало, что лигнификация клеточной стенки – одна из неспецифических реакций растений на этот и другие стрессоры, что ограничивает транспорт воды и ионов в тканях и целом растении. Настоящее исследование направлено на изучение реакции растений Zinnia elegans Jacq. на засоление в длительном эксперименте при выращивании на почве с регулярным поливом 50 мМ NaCl. Определены ростовые характеристики растений и биохимические показатели, такие как уровень пероксида водорода и малонового диальдегида (МДА), содержание фенольных соединений и лигнина. Уровень экспрессии генов, кодирующих биосинтез фенольных соединений и лигнина, оценивали по относительному количеству транскриптов. Внесение 50 mM NaCl в почву подавляло рост растений и индуцировало перекисное окисление липидов в тканях стебля, несмотря на увеличение концентрации фенольных соединений. Вероятно, их антиоксидантного потенциала было недостаточно для защиты растений. Количество лигнина в тканях стебля увеличивалось в основном за счет лигнина Класона, который ограничивал растяжение клеток. Уровень транскриптов генов PAL, C4H, 4CL, участвующих в синтезе фенольных соединений, коррелировал с повышением их концентрации; а генов CCR, CAD, PRX и LAC – с количеством лигнин

Regulation of expression of starch synthesis genes by ethylene and ABA in relation to the development of rice inferior and superior spikelets

Later-flowering spikelets in a rice panicle, referred to as the inferior spikelets, are usually poorly filled and often limit the yield potential of some rice cultivars. The physiological and molecular mechanism for such poor grain filling remains unclear. In this study the differentially expressed genes in starch synthesis and hormone signalling between inferior and superior spikelets were comprehensively analysed and their relationships with grain filling was investigated. DNA microarray and real-time PCR analysis revealed that a group of starch metabolism-related genes showed enhanced expression profiles and had higher transcript levels in superior spikelets than in inferior ones at the early and middle grain-filling stages. Expression of the abscisic acid (ABA) synthesis genes, 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED5, and the ethylene synthesis genes, 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) and ACO3, declined with development of the caryopses. Meanwhile, if compared with inferior spikelets, expression of these genes in superior spikelets decreased faster and had lower transcript profiles, especially for ethylene. ABA concentration and ethylene evolution rate showed similar trends to their gene expression. Exogenous supply of ABA reduced the sucrose synthase (SUS) mRNA level and its enzyme activity in detached rice grains, while exogenously supplied ethephon (an ethylene-releasing reagent) suppressed the expression of most starch synthesis genes; that is, SUS, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase (SSS), and down-regulated their enzyme activities. In summary, it is concluded that the relatively high concentrations of ethylene and ABA in inferior spikelets suppress the expression of starch synthesis genes and their enzyme activities and consequently lead to a low grain-filling rate

The role of the pod in seed development: strategies for manipulating yield

Pods play a key role in encapsulating the developing seeds and protecting them from pests and pathogens. In addition to this protective function, it has been shown that the photosynthetically active pod wall contributes assimilates and nutrients to fuel seed growth. Recent work has revealed that signals originating from the pod may also act to coordinate grain filling and regulate the reallocation of reserves from damaged seeds to those that have retained viability. In this review we consider the evidence that pods can regulate seed growth and maturation, particularly in members of the Brassicaceae family, and explore how the timing and duration of pod development might be manipulated to enhance either the quantity of crop yield or its nutritional properties