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This study investigated the accumulation of phenlyacetaldoxime (PAOx) and PAOx-Glc in Tococa quadrialata leaves in response to herbivore infestation and mechanical wounding. Results show that PAOx levels peaked at 24 h post-infestation, while PAOx-Glc remained present for several days. The accumulation of PAOx began as early as 3 h after herbivory, with PAOx-Glc significantly increased after 6 h. Mechanical wounding induced similar responses in PAOx and PAOx-Glc accumulation as herbivory, suggesting that continuous tissue damage triggers the production of these compounds. Interestingly, SpitWorm-treated leaves showed the highest levels of both PAOx and PAOx-Glc, indicating that herbivore-derived oral secretions (OS) play a role in the induction of these compounds. Additionally, JA-independent PAOx production was found to be associated with tissue damage rather than specific known signaling compounds. Emission of benzyl cyanide and 2-phenylethanol, PAOx-derived plant volatiles, was observed in response to herbivory and SpitWorm treatment providing plant-derived OS, further highlighting the role of herbivore cues in plant defense responses.

Due to the involvement of calcium as a main second messenger in the plant signaling pathway, increasing interest has been focused on the calcium signatures supposed to be involved in the patterning of the specific response associated to a given stimulus. In order to follow these signatures we described here the practical approach to use the non-invasive method based on the aequorin technology. Besides reviewing the advantages and disadvantages of this method we report on results showing the usefulness of aequorin to study the calcium response to biotic (elicitors) and abiotic stimuli (osmotic shocks) in various compartments of plant cells such as cytosol and nucleus.

Plants assimilate inorganic nitrogen (N) to glutamine. Glutamine is the most abundant amino acid in most plant species, the N-supplying precursor of all N-containing compounds in the cell and the first organic nitrogen molecule formed from inorganic nitrogen taken up by the roots. In addition to its role in plant nutrition, glutamine most likely also has a function as a signaling molecule in the regulation of nitrogen metabolism. We investigated whether glutamine influences the high-affinity transporter system for nitrate uptake. Therefore, we analyzed the expression of the nitrate transporter NRT2.4, which is inducible by N deficiency, in Arabidopsis thaliana grown under different nitrogen starvation scenarios, comparing nitrate or glutamine as the sole nitrogen source. Using the reporter line ProNRT2.4:GFP and two independent knockout lines, nrt2.4-1 and nrt2.4-2, we analyzed gene expression and amino acid profiles. We showed that the regulation of NRT2.4 expression depends on available nitrogen in general, for example on glutamine as a nitrogen source, and not specifically on nitrate. In contrast to high nitrate concentrations, amino acid profiles changed to an accumulation of amino acids containing more than one nitrogen during growth in high glutamine concentrations, indicating a switch to nitrogen storage metabolism. Furthermore, we demonstrated that the nrt2.4-2 line shows unexpected effects on NRT2.5 gene expression and the amino acids profile in shoots under high glutamine supply conditions compared to Arabidopsis wild type and nrt2.4-1, suggesting non-NRT2.4-related metabolic consequences in this knockout line.

Abstract Date palm (Phoenix dactylifera L.) is able to grow and complete its life cycle while being rooted in highly saline soils. Which of the many well‐known salt‐tolerance strategies are combined to fine‐tune this remarkable resilience is unknown. The precise location, whether in the shoot or the root, where these strategies are employed remains uncertain, leaving us unaware of how the various known salt‐tolerance mechanisms are integrated to fine‐tune this remarkable resilience. To address this shortcoming, we exposed date palm to a salt stress dose equivalent to seawater for up to 4 weeks and applied integrative multi‐omics analyses followed by targeted metabolomics, hormone, and ion analyses. Integration of proteomic into transcriptomic data allowed a view beyond simple correlation, revealing a remarkably high degree of convergence between gene expression and protein abundance. This sheds a clear light on the acclimatization mechanisms employed, which depend on reprogramming of protein biosynthesis. For growth in highly saline habitats, date palm effectively combines various salt‐tolerance mechanisms found in both halophytes and glycophytes: “avoidance” by efficient sodium and chloride exclusion at the roots, and “acclimation” by osmotic adjustment, reactive oxygen species scavenging in leaves, and remodeling of the ribosome‐associated proteome in salt‐exposed root cells. Combined efficiently as in P. dactylifera L., these sets of mechanisms seem to explain the palm's excellent salt stress tolerance.

Abstract Background Though many abiotic factors are constantly changing, the photoperiod is a predictable factor that enables plants to time many physiological responses. This timing is regulated by the circadian clock, yet little is known about how the clock adapts to the differences in photoperiod between mid-latitudes and high latitudes. The primary objective of this study was to compare how clock gene expression is modified in four woodland strawberry (Fragaria vesca L.) accessions originating from two different populations in Italy (IT1: Tenno, Italy, 45°N, IT4: Salorno, Italy, 46°N) and two in Northern Norway (NOR2: Alta, Norway, 69°N, NOR13: Indre Nordnes, Norway 69°N) when grown under simulated daylength conditions of an Arctic or mid-latitude photoperiod. The second objective was to investigate whether population origin or the difference in photoperiod influenced phytohormone accumulation. Results The Arctic photoperiod induced lower expression in IT4 and NOR13 for six clock genes (FvLHY, FvRVE8, FvPRR9, FvPRR7, FvPRR5, and FvLUX), in IT1 for three genes (FvLHY, FvPRR9, and FvPRR5) and in NOR2 for one gene (FvPRR9). Free-running rhythms for FvLHY in IT1 and IT4 were higher after the Arctic photoperiod, while the free-running rhythm for FvLUX in IT4 was higher after the mid-latitude photoperiod. IT1 showed significantly higher expression of FvLHY and FvPRR9 than all other accessions, as well as significantly higher expression of the circadian regulated phytohormone, abscisic acid (ABA), but low levels of salicylic acid (SA). NOR13 had significantly higher expression of FvRVE8, FvTOC1, and FvLUX than all other accessions. NOR2 had extremely low levels of auxin (IAA) and high levels of the jasmonate catabolite, hydroxyjasmonic acid (OH-JA). Conclusions Our study shows that circadian rhythms in Fragaria vesca are driven by both the experienced photoperiod and genetic factors, while phytohormone levels are primarily determined by specific accessions’ genetic factors rather than the experienced photoperiod.

AbstractIn the wake of climate change, failing of conventional food systems, and low agricultural productivity, baobab tree is central to the livelihoods of many individuals in ASALs. In Kenya, the baobab is a high-priority tree with high economic value than use value. However, products derived from the tree remain rare and only a few are traded. This paper sought to establish the determinants of awareness and attitudes of retailers toward baobab products. Descriptive statistics, Zero-truncated Poisson model, and Exploratory factor analysis were employed to assess awareness levels, attitudes, and their underlying determinants. Data was collected from 352 retailers in rural and urban markets. Descriptive indicated a low product awareness across markets. Further, attitudes of retailers towards baobab were positive and relatively homogeneous. Out of the 13 statements, 10 scored positively on the Likert scale. The model revealed that gender, age, education, years in retailing, and group membership positively influenced awareness, while distance to the market and income from other sources had a negative influence. Exploratory factor analysis generated five factors that explained 57.93% of the total variance. “Source of employment”, “livelihood and survival”, and “nutritive value and freshness,” had the highest factor loadings respectively. The study, therefore, recommends the need to develop strategies that could promote awareness of baobab products. This includes; designing appropriate educational and training programs that focus on gender disparity, youth, and nutritional value. Likewise, governments and the private sector should invest in baobab value chain and infrastructure to enhance market employability, access and availability of products.

Carnivorous plants reverse the order we expect in nature: here, animals do not feed on plants, but plants hunt and feed on animal prey, primarily insects, thereby enabling these plants to survive in nutrient-poor environments. In addition to this strategy, some carnivorous plants also form unique symbiotic relationships with animals other than insects to access nutrients. Other important interactions of carnivorous plants with insects, such as pollinators and herbivores, have received far less attention or have been largely neglected. This review describes and summarizes various ecologically relevant biotic interactions between carnivorous plants and other organisms reported in recent studies. In particular, our understanding on how carnivorous plants, for example, handle the pollinator–prey-conflict or interact with and respond to herbivores is still incomplete. Strategies and mechanisms on how carnivorous plants address these challenges are presented. Finally, future directions in carnivorous plant research are proposed.

IntroductionWild fruits like Baobab are gaining status as a valuable food resource worldwide. As with other crops, the reduction of post-harvest losses is critical to enhancing sustainable utilisation of wild food resources. However, little information is documented on the magnitude and determinants of post-harvest losses (PHLs) amongst Non-Timber Forest Products (NTFPs), and baobab in particular.MethodsThis study used cross-sectional data collected from six districts to analyse PHLs along the baobab value chain in Malawi. A multistage sampling technique was used to sample 405 collectors, 96 traders, and 316 processors. Two-limit Tobit models were used to ascertain correlates of PHLs at each value chain level. The study quantified the value of PHLs and assessed the effect of socioeconomic factors on PHLs amongst baobab actors.ResultsWe found that actors in the baobab value chain lose 7.78% of the total value of products held through PHLs. The results also showed that different sets of socioeconomic factors variably influenced PHLs amongst different value chain actors in the baobab value chain. For instance, gender was found to only correlate with PHLs amongst collectors. Whilst marital status was positively correlated with PHLs amongst collectors, and had a negative relationship amongst processors. PHLs at traders’ level are influenced by the number of people employed by an actor, the ability of customers to specify product attributes, and a proportional reduction in sales volume due to COVID-19. The study recommends the provision of training in PHLs management, and the formulating and enforcing of Baobab product handling standards.

There are growing number of empirical studies on the baobab value chain in Sub-Saharan Africa. Most studies focus on nutritional composition, traditional uses, the distribution of baobab trees, and collection. However, there are few studies on the marketing of baobab fruit pulp, especially on consumer behavior, attitudes, and beliefs regarding baobab fruit pulp. In this context, our study aims to explore consumer behavior, attitudes and beliefs regarding baobab fruit pulp. We also evaluate the market development potential of baobab fruit pulp in selected markets in El Obeid and Khartoum in Sudan. The study employs a mixed methods approach that includes a survey (N = 499), focus group discussion (N = 16), stakeholder interviews (N = 2), and a SWOT analysis. The study shows that the consumption of baobab fruit pulp is common among Sudanese consumers. Consumers also show strong positive attitudes and beliefs, as well as social support for baobab consumption. Nutritional and health benefits tend to drive consumer interest in baobab fruit pulp. The study also identified high demand, export opportunities, and extraction of ingredients from baobab as opportunities to develop baobab markets. However, a lack of quality control, regulations, poor distribution, and insufficient fruit supply may limit exploration of these opportunities. Therefore, it is crucial to raise knowledge of the nutritional and functional properties of baobab fruit, as well as its ability to fight health-related diseases, to further develop local markets. Processors must also improve the quality and safety of their goods. Policymakers must also create a regulatory structure that supports Sudan’s baobab value chain.

The value chains of African indigenous vegetables (AIVs) are highly constrained by high postharvest losses (up to 50%) along the chain, largely occasioned by poor postharvest management and a lack of optimized processing technologies. The technologies and practices are key technical aspects that can transform the capacity of the chain by enhancing the overall value generated from the system. AIVs have recently experienced an increase in demand due to their high nutritional value and the opportunity they present to enhance rural incomes, since they are predominantly produced by smallholder farmers in rural and peri-urban areas. This implies that they can positively contribute to increased availability and hence supply of nutritious food within local food systems. Furthermore, the fact that half of the economic value of AIVs is potentially lost due to inappropriate postharvest management and inadequate processing demonstrates the potential that related interventions and transformations could have in enhancing and preserving value along AIV value chains. Currently, the approaches applied to reduce food waste, preserve nutritional quality, and add value to AIVs are largely traditional in nature. They require upgrading and need to be aligned toward achieving a nutrition-sensitive value chain. By looking at these as value creation processes, this mini-review examines the current postharvest management practices, highlights relevant new and innovative technologies and related challenges, and suggests potential options to improve the benefits for AIV value chain actors and thus contribute to a sustainable transformation of nutrition-sensitive food systems.

Abstract Microbial volatiles are important factors in symbiotic interactions with plants. Mortierella hyalina is a beneficial root-colonizing fungus with a garlic-like smell, and promotes growth of Arabidopsis seedlings. GC–MS analysis of the M. hyalina headspace and NMR analysis of the extracted essential oil identified the sulfur-containing volatile tris(methylthio)methane (TMTM) as the major compound. Incorporation of the sulfur from the fungal volatile into plant metabolism was shown by 34S labeling experiments. Under sulfur deficiency, TMTM down-regulated sulfur deficiency-responsive genes, prevented glucosinolate (GSL) and glutathione (GSH) diminishment, and sustained plant growth. However, excess TMTM led to accumulation of GSH and GSL and reduced plant growth. Since TMTM is not directly incorporated into cysteine, we propose that the volatile from M. hyalina influences the plant sulfur metabolism by interfering with the GSH metabolism, and alleviates sulfur imbalances under sulfur stress.

The Kenyan mango value chain faces high post-harvest losses due to poor market access alongside a lack of storage technologies and processing facilities. Thus, using fruit processing methods, like solar drying, can enhance shelf life and help smallholder farmers access new markets, diversifying income and livelihoods. Nonetheless, the processing of both indigenous and grafted mango fruits is not a very common practice. This study was conducted to support product development targeting processing and marketing to link farmers to both local and export markets. Four independent consumer testing and sensory evaluation rounds on Kitui’s dried mango flakes were conducted in Germany and Kenya. Data were collected via a group tasting by 31 randomly selected participants and an online questionnaire of 304 randomly selected participants. All participants were given samples of different varieties of dried mango flakes with and without additives. Results show that high-quality mango cultivars, like Ngowe, receive high hedonic scores without any additives (honey, sodium metabisulfite, or ascorbic acid). Some varieties positively respond to the treatments and achieve higher scores, e.g., Van Dyke or the indigenous variety Kikamba. The consumers testing in Germany show that extrinsic attributes, such as organic production, fair trade, cooperative, and sustainable labelled flakes open up new opportunities for farmers who aim for the export market. Against findings derived from German panellists, in Kenya, consumers do not show a higher willingness to pay despite having a positive attitude toward sustainability. Thus, the local market should focus on cost-reduction strategies rather than introducing standardisation.

One of the major impacts of climate change is increasing global temperatures. Because warming is expected to affect plant morphological and chemical traits, it may therefore also influence plant interactions with other trophic levels, including herbivores. Here, we simulated a climate warming scenario of +2.7°C in the field using open-top chambers and assessed the effects of warming on plant performance (growth, leaf area, and chlorophyll), leaf nutrients (nitrogen and carbon), and primary (amino acids and carbohydrates) and secondary (toxic aristolochic acids) metabolites in the plant Aristolochia chilensis. We performed untargeted metabolomics analyses for estimating general changes in foliar metabolites between ambient control and warming-treated plants. Bioassays were additionally conducted to evaluate how changes in host plant chemistry affected growth and nutritional parameters in first-instar larvae of the specialist lepidopteran herbivore Battus polydamas archidamas. We found that warming did not significantly affect plant performance, but did result in significant changes in leaf nutrients, and primary and secondary metabolites, although in opposite directions. While primary metabolites (specifically, nitrogen-containing compounds) decreased in response to treatment, aristolochic acids increased. Untargeted metabolomics analyses showed that, of a total of 824 features, 50 were significantly different between ambient control and warming-treated plants; some of these were identified by MS/MS spectra as amino acids. Larvae feeding on warming-treated plants, showed significantly enhanced growth, food conversion efficiency, and lipid concentration. Our study contributes to current understanding of climate change impacts on trophic interactions, showing that projected temperature increases lead to changes in the resistance phenotype of the host plant, favoring nutrition and growth of a unique specialist herbivore.

Yellow to red colored betalains are a chemotaxonomic feature of Caryophyllales, while in most other plant taxa, anthocyanins are responsible for these colors. The carnivorous plant family Nepenthaceae belongs to Caryophyllales; here, red‐pigmented tissues seem to attract insect prey. Strikingly, the chemical nature of red color in Nepenthes has never been elucidated. Although belonging to Caryophyllales, in Nepenthes, some molecular evidence supports the presence of anthocyanins rather than betalains. However, there was previously no direct chemical proof of this. Using ultra‐high‐performance liquid chromatography‐electrospray ionization‐high‐resolution mass spectrometry, we identified cyanidin glycosides in Nepenthes species and tissues. Further, we reveal the existence of a complete set of constitutively expressed anthocyanin biosynthetic genes in Nepenthes. Thus, here we finally conclude the long‐term open question regarding red pigmentation in Nepenthaceae.

Global warming is predicted to change the growth conditions for plants and crops in regions at high latitudes (>60° N), including the Arctic. This will be accompanied by alterations in the composition of natural plant and pest communities, as herbivorous arthropods will invade these regions as well. Interactions between previously non-overlapping species may occur and cause new challenges to herbivore attack. However, plants growing at high latitudes experience less herbivory compared to plants grown at lower latitudes. We hypothesize that this finding is due to a gradient of constitutive chemical defense towards the Northern regions. We further hypothesize that higher level of defensive compounds is mediated by higher level of the defense-related phytohormone jasmonate. Because its biosynthesis is light dependent, Arctic summer day light conditions can promote jasmonate accumulation and, hence, downstream physiological responses. A pilot study with bilberry (Vaccinium myrtillus) plants grown under different light regimes supports the hypothesis.

Summary: Ant-plant defensive mutualism is a widely studied phenomenon, where ants protect their host plants (myrmecophytes) against herbivores in return for the provision of nesting sites and food. However, few studies addressed the influence of ant colonization and herbivory on the plant’s metabolism. We chose the Amazonian plant Tococa quadrialata, living in association with Azteca cf. tonduzi ants for an ant-exclusion study to reveal the chemistry behind this symbiosis. We found that colonized plants did not only benefit from protection but also from increased amino acid and nitrogen content, enabling better performance even in an herbivore-free environment. In contrast, ant-deprived T. quadrialata plants accumulated more ellagitannins, a major class of constitutive defense compounds. Moreover, herbivory-induced jasmonate-mediated defense responses, including the upregulation of signaling and defense genes and the emission of volatiles irrespective of colonization status. Altogether, we show how ant-colonization can influence the general and defense-related metabolism and performance of myrmecophytes.

General volatile anesthetic diethyl ether blocks sensation and responsive behavior not only in animals but also in plants. Here, using a combination of RNA-seq and proteomic LC–MS/MS analyses, we investigated the effect of anesthetic diethyl ether on gene expression and downstream consequences in plant Arabidopsis thaliana. Differential expression analyses revealed reprogramming of gene expression under anesthesia: 6,168 genes were upregulated, 6,310 genes were downregulated, while 9,914 genes were not affected in comparison with control plants. On the protein level, out of 5,150 proteins identified, 393 were significantly upregulated and 227 were significantly downregulated. Among the highest significantly downregulated processes in etherized plants were chlorophyll/tetrapyrrole biosynthesis and photosynthesis. However, measurements of chlorophyll a fluorescence did not show inhibition of electron transport through photosystem II. The most significantly upregulated process was the response to heat stress (mainly heat shock proteins, HSPs). Using transgenic A. thaliana expressing APOAEQUORIN, we showed transient increase of cytoplasmic calcium level [Ca2+]cyt in response to diethyl ether application. In addition, cell membrane permeability for ions also increased under anesthesia. The plants pre-treated with diethyl ether, and thus with induced HSPs, had increased tolerance of photosystem II to subsequent heat stress through the process known as cross-tolerance or priming. All these data indicate that diethyl ether anesthesia may partially mimic heat stress in plants through the effect on plasma membrane.

Baobab is an iconic tree that is utilized as a source of food and income generation. While extant literature on baobab has focused on its morphological attributes and nutrient composition, there is a gap in literature in understanding the characteristics of processors and the factors that determine baobab processing. Using cross section data of 304 baobab processors in Kenya, we employ Principal Component Analysis and Cluster Analysis to characterize baobab processors and identify determinants of baobab processing. Results of processed volumes show that baobab processors are grouped in three clusters of high, average and low categories. Clusters of processors are shaped by number of years in processing, access to training, quantity processed, processing cost, income from other sources, access to land, and profit levels. The study suggests the need to train processors on baobab processing to increase their efficiency and returns. Through training, processors will be able to make informed decisions on input use, packaging and presentation of their products to the customers. Also, investment in baobab conservation, harvesting more trees and reducing the maturity rate of the baobab trees will increase baobab inputs thus lowering processing cost.

Abstract Gender gaps in agrifood value chains are manifested in differential access to and control of productive resources, upgrading activities, market participation, farm productivity and food security among women and men. These gender gaps threaten economic development in sub‐Saharan Africa. With low‐resource requirements, edible insects have emerged as a promising agrifood value chain with income opportunities for women and men. However, it is not clear how gender gaps are manifested in the participation in value addition and lean season market of the edible insect value chain with a potential to improve household welfare. In this paper, we analyse the gender gaps of retailers' participation in value addition and lean season market in the grasshopper value chain in Uganda. Multivariate probit and tobit models are used in the empirical analyses. We find that women are 15% more likely to participate in primary value addition. However, there are no gender gaps in the participation in secondary value addition and the lean season market. The study also shows that grasshopper business is an important source of income for many retailers. Therefore, the development of the grasshopper value chain, especially the aspects of value addition and lean season market, could contribute to gender equality and improvement of livelihoods of women and men.

Empirical studies show that smallholder farmers can benefit from collective action by improving their crop production and access to better markets. Although there are numerous studies on the effects of collective action on production and marketing of staple crops, such studies, particularly on the analysis of gender and collective action, are scarce for underutilized crops such as baobab. To address this gap, we estimate the impacts of cooperative membership on baobab income and food security, using data collected from a survey of 864 baobab collectors in Malawi. We employ the Inverse Probability Weight Regression Adjustment estimator to account for selection bias. We also analyse heterogeneity in the impact of cooperatives attributable to gender. We find that cooperative membership increases baobab income, household dietary diversity score, and food consumption score by 3.57%, 11%, and 5.6%, respectively. However, the welfare outcome of cooperative members differs based on gender. In particular, households with male baobab managers that are cooperative members have higher income and are more food secure. Households with unmarried female managers have better welfare outcomes. The results, therefore, highlight the need to promote collective action through cooperatives in the underutilized crop sector to enhance household welfare. [ABSTRACT FROM AUTHOR]

Plants assimilate inorganic nitrogen (N) to glutamine. Glutamine is the most abundant amino acid in most plant species, the N-supplying precursor of all Ncontaining compounds in the cell and the first organic nitrogen molecule formed from inorganic nitrogen taken up by the roots. In addition to its role in plant nutrition, glutamine most likely also has a function as a signaling molecule in the regulation of nitrogen metabolism. We investigated whether glutamine influences the high-affinity transporter system for nitrate uptake. Therefore, we analyzed the expression of the nitrate transporter NRT2.4, which is inducible by N deficiency, in Arabidopsis thaliana grown under different nitrogen starvation scenarios, comparing nitrate or glutamine as the sole nitrogen source. Using the reporter line ProNRT2.4:GFP and two independent knockout lines, nrt2.4-1 and nrt2.4-2, we analyzed gene expression and amino acid profiles. We showed that the regulation of NRT2.4 expression depends on available nitrogen in general, for example on glutamine as a nitrogen source, and not specifically on nitrate. In contrast to high nitrate concentrations, amino acid profiles changed to an accumulation of amino acids containing more than one nitrogen during growth in high glutamine concentrations, indicating a switch to nitrogen storage metabolism. Furthermore, we demonstrated that the nrt2.4-2 line shows unexpected effects on NRT2.5 gene expression and the amino acids profile in shoots under high glutamine supply conditions compared to Arabidopsis wild type and nrt2.4-1, suggesting non-NRT2.4-related metabolic consequences in this knockout line. [ABSTRACT FROM AUTHOR]

The degradation of cellulose generates cellooligomers, which function as damage-associated molecular patterns and activate immune and cell wall repair responses via the CELLOOLIGOMER RECEPTOR KINASE1 (CORK1). The most active cellooligomer for the induction of downstream responses is cellotriose, while cellobiose is around 100 times less effective. These short-chain cellooligomers are also metabolized after uptake into the cells. In this study, we demonstrate that CORK1 is mainly expressed in the vascular tissue of the upper, fully developed part of the roots. Cellooligomer/CORK1-induced responses interfere with chitin-triggered immune responses and are influenced by BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE1 and the receptor kinase FERONIA. The pathway also controls sugar transporter and metabolism genes and the phosphorylation state of these proteins. Furthermore, cellotriose-induced ROS production and WRKY30/40 expression are controlled by the sugar transporters SUCROSE-PROTON SYMPORTER1, SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTER11 (SWEET11), and SWEET12. Our data demonstrate that cellooligomer/CORK1 signaling is integrated into the pattern recognition receptor network and coupled to the primary sugar metabolism in Arabidopsis roots. [ABSTRACT FROM AUTHOR]

The host-pathogen combinations-Malus domestica (apple)/`Candidatus Phytoplasma mali´, Prunus persica (peach)/`Ca. P. prunorum´ and Pyrus communis (pear)/`Ca. P. pyri´ show different courses of diseases although the phytoplasma strains belong to the same 16SrX group. While infected apple trees can survive for decades, peach and pear trees die within weeks to few years. To this date, neither morphological nor physiological differences caused by phytoplasmas have been studied in these host plants. In this study, phytoplasma-induced morphological changes of the vascular system as well as physiological changes of the phloem sap and leaf phytohormones were analysed and compared with non-infected plants. Unlike peach and pear, infected apple trees showed substantial reductions in leaf and vascular area, affecting phloem mass flow. In contrast, in infected pear mass flow and physicochemical characteristics of phloem sap increased. Additionally, an increased callose deposition was detected in pear and peach leaves but not in apple trees in response to phytoplasma infection. The phytohormone levels in pear were not affected by an infection, while in apple and peach trees concentrations of defence- and stress-related phytohormones were increased. Compared with peach and pear trees, data from apple suggest that the long-lasting morphological adaptations in the vascular system, which likely cause reduced sap flow, triggers the ability of apple trees to survive phytoplasma infection. Some phytohormone-mediated defences might support the tolerance.