Basal Plant Research Articles

SYNTAXIN OF PLANTS 132 underpins secretion of cargoes associated with salicylic acid signaling and pathogen defense.

Secretory trafficking in plant cells is facilitated by SNARE (soluble N-ethylamide-sensitive factor attachment protein receptor) proteins that drive membrane fusion of cargo-containing vesicles. In Arabidopsis, SYNTAXIN OF PLANTS 132 (SYP132) is an evolutionarily ancient SNARE that functions with syntaxins SYP121 and SYP122 at the plasma membrane. Whereas SYP121 and SYP122 mediate overlapping secretory pathways, albeit with differences in their importance in plant-environment interactions, the SNARE SYP132 is absolutely essential for plant development and survival. SYP132 promotes endocytic traffic of the plasma membrane H+-ATPase AHA1 and aquaporin PIP2;1, and it coordinates plant growth and bacterial pathogen immunity through PATHOGENESIS-RELATED1 (PR1) secretion. Yet, little else is known about SYP132 cargoes. Here, we used advanced quantitative Tandem Mass Tagging (TMT) mass spectrometry (MS) combined with immunoblot assays to track native secreted cargo proteins in the leaf apoplast. We found that SYP132 supports a basal level of secretion in Arabidopsis leaves, and its overexpression influences salicylic acid (SA) and jasmonic acid (JA) defence-related cargoes including PR1, PR2, and PR5 proteins. Impairing SYP132 function also suppressed defence-related secretory traffic when challenged with the bacterial pathogen Pseudomonas syringae. Thus, we conclude that, in addition to its role in hormone-related H+-ATPase cycling, SYP132 influences basal plant immunity.

Initiation of Cassava Callus Culture and Its Prospect for Starch Production: A Systematic Mapping Study

Mass propagation of cassava on several hectares of arable land due to increasing demand for its starch is not feasible due to land availability, pests and disease invasion, and long cultivation period. Plant cell culture technology is a promising solution despite the scarcity of cassava callus culture for starch production applications. Therefore, a systematic mapping study (SMS) was performed to identify the applications of cassava tissue culture and its prospects in starch production and investigate the important parameters for cassava callus culture initiation. The SMS began with formulating research questions (RQs), conducting searches on various databases, collecting and screening related articles, and extracting and mapping the selected articles. A total of 56 of 589 articles in the initial searching phase were chosen to be used as references to answer each RQ. The extracted data indicates that cassava tissue culture was mostly used for micropropagation, while starch production from its tissue culture is still limited. Basal medium and plant growth regulators influence cassava callus culture initiation most. The findings of the SMS offer a better understanding of cassava tissue culture and the prospects of producing cassava starch.

Botrytis cinerea combines four molecular strategies to tolerate membrane-permeating plant compounds and to increase virulence

Saponins are plant secondary metabolites comprising glycosylated triterpenoids, steroids or steroidal alkaloids with a broad spectrum of toxicity to microbial pathogens and pest organisms that contribute to basal plant defense to biotic attack. Secretion of glycosyl hydrolases that enzymatically convert saponins into less toxic products was thus far the only mechanism reported to enable fungal pathogens to colonize their saponin-containing host plant(s). We studied the mechanisms that the fungus Botrytis cinerea utilizes to be tolerant to well-characterized, structurally related saponins from tomato and Digitalis purpurea. By gene expression studies, comparative genomics, enzyme assays and testing a large panel of fungal (knockout and complemented) mutants, we unraveled four distinct cellular mechanisms that participate in the mitigation of the toxic activity of these saponins and in virulence on saponin-producing host plants. The enzymatic deglycosylation that we identified is novel and unique to this fungus-saponin combination. The other three tolerance mechanisms operate in the fungal membrane and are mediated by protein families that are widely distributed in the fungal kingdom. We present a spatial and temporal model on how these mechanisms jointly confer tolerance to saponins and discuss the repercussions of these findings for other plant pathogenic fungi, as well as human pathogens.

Marchantia polymorpha GOLDEN2-LIKE transcriptional factor; acentral regulator of chloroplast and plant vegetative development.

The GOLDEN2-LIKE (GLK) transcription factors act as a central regulatory node involved in both developmental processes and environmental responses. Marchantia polymorpha, a basal terrestrial plant with strategic evolutionary position, contains a single GLK representative that possesses an additional domain compared to spermatophytes. We analyzed the role of MpGLK in chloroplast biogenesis and development by altering its levels, preforming transcriptomic profiling and conducting chromatin immunoprecipitation. Decreased MpGLK levels impair chloroplast differentiation and disrupt the expression of photosynthesis-associated nuclear genes, while overexpressing MpGLK leads to ectopic chloroplast biogenesis. This demonstrates the MpGLK functions as a bona fide GLK protein, likely representing an ancestral GLK architecture. Altering MpGLK levels directly regulates the expression of genes involved in Chl synthesis and degradation, similar to processes observed in eudicots, and causes various developmental defects in Marchantia, including the formation of dorsal structures such as air pores and gemma cups. MpGLK, also directly activates MpMAX2 gene expression, regulating the timing of gemma cup development. Our study shows that MpGLK functions as a master regulator, potentially coupling chloroplast development with vegetative reproduction. This illustrates the complex regulatory networks governing chloroplast function and plant development communication and highlight the evolutionary conservation of GLK-mediated regulatory processes across plant species.

Dihydrogibberellin improves grain yield and lodging resistance of direct seeded rice

AbstractDihydrogibberellin (DIH) is an eco‐friendly and low‐toxic regulator with immense potential for application in the current rice industry, specifically for increasing yield and lodging resistance. However, limited research has been conducted to explore the impact of DIH on the yield and lodging resistance of direct‐seeded rice (DSR, Oryza sativa L.). Therefore, a 2‐year field experiment was conducted to evaluate the effects of spraying different concentrations of 5% DIH emulsifiable concentrate on DSR during the tillering (1) and jointing (2) stages. Three concentrations of DIH were used: 27 (DIH27), 54 (DIH54), and 108 g ha−1 (DIH108). The commonly used paclobutrazol concentration in rice production (112.5 g ha−1) was compared and a clear water treatment was used as control (CK). The results of the experiment showed that the DIH treatments increased the DSR yield by 1.22%–22.64% and reduced lodging index by 8.9%–54.2% compared to the CK treatment. Additionally, the DIH treatments resulted in significant reductions in the length of the 1–3 basal internodes and plant height, as well as increases in the diameter and culm wall thickness of internodes. Moreover, the DIH treatments also led to higher dry matter percentages in stalks and leaf sheaths, as well as increased lignin and cellulose content. Furthermore, the best effect of DIH application was observed at the jointing stage in terms of increasing yield and lodging resistance. Therefore, this research demonstrates that the application of DIH to DSR at the jointing stage can be an effective strategy for increasing yield and improving lodging resistance.

Seed Propagation of Carapa amorphocarpa W. Palacios Using Various Treatments of Substrates and Mechanical Seed Scarification in a Nursery in the Andean Area of Northwestern Ecuador

Carapa amorphocarpa W. Palacios is a forest species known solely from Cerro Golondrinas in northwestern Ecuador. The species is threatened due to illegal exploitation of its wood and the encroachment of the agricultural frontier. Although information on its ecology and forestry was presented in 2012, there is still very little information available. This study investigated the effects of various pre-germinative treatments on the seed germination and early growth of Carapa amorphocarpa in a nursery. The treatments included combinations of substrates (forest soil alone and forest soil mixed with sand), along with pre-germinative mechanical seed scarification. Through these treatments, the seeds’ germination capacity, growth potential, and survival rates were evaluated in a nursery. Seed germination was found to be cryptocotylar hypogeal, commencing at 41 days and achieving an average of 83.13%. Survival of germinated seedlings was 99.23% at 60 days after germination. Furthermore, a high degree of correlation in growth was observed between basal diameter and plant height (R = 0.94). The mean values for the plants’ basal diameter and total height were 0.91 cm and 50.48 cm, respectively, at 60 days. Plant form was straight with excellent health. These insights offer the potential to enhance species populations, mitigate threat risks, and in the long term, foster sustainable use of Carapa amorphocarpa genetic resources. Moreover, this seed propagation information can be leveraged for other species within the genus exploited for oil extraction from their seeds, thereby broadening knowledge and facilitating sustainable forest resource management.

Effective, Consistent, and Rapid Noncontact Application Methods for Seedling Basal Stem Infection by Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum (Lib.) de Bary, an economically devastating soilborne fungal pathogen known to cause disease across a wide range of plants, produces long-term inoculum called sclerotia that can germinate either carpogenically by ascospores infecting aboveground plant parts or myceliogenically to infect stem base and roots. Typically, for research purposes, S. sclerotiorum diseases are initiated by direct contact methods, using S. sclerotiorum mycelium agar plugs wrapped around the stem or sclerotia placed directly beneath root mass. However, reproducible noncontact methods leading to basal stem infection are not currently available. Therefore, the objective of this study was to develop effective noncontact protocols that consistently generate basal plant stem infection from S. sclerotiorum in the soil. Using three host plant species (canola, lupin, and lettuce), we determined two methods that reliably produced basal stem infection. The first method, where mycelial agar plugs were positioned just below the soil surface at a distance of 5 mm from each seedling, led to 100% infection in all plants. The second method used pathogen-infested soil by mixing the soil with dry inoculum in the form of a powder prepared from mycelium-colonized organic substrates. Four substrates consistently produced 100% seedling infection at 4 days after inoculation (DAI): wheat bran, wheat grain, red rice, and hulled millet. In contrast, chia, canary, sesame, and ryegrass seed substrates resulted in less than 50% seedling infection at 10 DAI, and infection levels did not progress further. The two soil inoculation methods outlined in this study will enhance future research on the progression of S. sclerotiorum diseases, with the potential to screen disease-resistant host genotypes to basal S. sclerotiorum infection and, in particular, to test the effectiveness of soil applications of fungicides or biocontrol agents against S. sclerotiorum basal infection.

The transcription factor MYB1 activates DGAT2 transcription to promote triacylglycerol accumulation in sacha inchi (Plukenetia volubilis L.) leaves under heat stress

Triacylglycerol (TAG) accumulation is frequently triggered in vegetative tissues experiencing heat stress, which may increases plant basal plant thermo-tolerance by sequestering the toxic lipid intermediates that contribute to membrane damage or cell death under stress conditions. However, stress-responsive TAG biosynthesis and the underlying regulatory mechanisms are not fully understood. Here, we investigated the lipidomic and transcriptomic landscape under heat stress in the leaves of sacha inchi (Plukenetia volubilis L.), an important oilseed crop in tropical regions. Under heat stress (45 °C), the content of polyunsaturated TAGs (e.g., TAG18:2 and TAG18:3) and total TAGs were significantly higher, while those of unsaturated sterol esters, including ZyE 28:4, SiE 18:2 and SiE 18:3, were dramatically lower. Transcriptome analysis showed that the expression of PvDGAT2-2, encoding a type II diacylglycerol acyltransferase (DGAT) that is critical for TAG biosynthesis, was substantially induced under heat stress. We confirmed the function of PvDGAT2-2 in TAG production by complementing a yeast mutant defective in TAG biosynthesis. Importantly, we also identified the heat-induced transcription factor PvMYB1 as an upstream activator of PvDGAT2-2 transcription. Our findings on the molecular mechanism leading to TAG biosynthesis in leaves exposed to heat stress have implications for improving the biotechnological production of TAGs in vegetative tissues, offering an alternative to seeds.

Identification and characterization of lettuce cultivars with high inhibitory activity against the human pathogen Escherichia coli O157:H7: Toward a plant-intrinsic hurdle approach to microbial safety

Foodborne illness linked to fruit and vegetables poses a major challenge to public health and horticulture production. Processed lettuce has been implicated in recurrent outbreaks of pathogenic Shiga toxin-producing Escherichia coli (STEC) infection. We hypothesized that plant defenses elicited by mechanical injury may effect STEC inhibition in cut leaves. Intact and cut leaves of 31 lettuce cultivars (Lactuca spp.) selected from >500 accessions based on their resistance to common insect pests and the necrotrophic lettuce drop pathogen were assessed for STEC serovar O157:H7 (EcO157) survival under cold storage conditions. The cultivars were previously ranked also for phenotypes such as resistance to other phytopathogens and physiological traits. Total leaf phenolic compounds, anthocyanins, and reactive oxygen species (ROS); and phenylalanine lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO) activity were quantified in each cultivar. Principal Component Analysis (PCA) and K-means cluster analysis were applied to group phenotypes and EcO157 population decline on lettuce. In five cultivars, high resistance to herbivorous insects (aphids, leaf miners and thrips), diseases (lettuce drop, downy mildew, and Impatiens Necrotic Spot Virus), and the disorder tipburn was associated with up to 42-fold EcO157 population decline on cold-stored cut (shredded) leaves, and with up to 11-fold difference in decline on cold-stored intact vs cut leaves (ΔD). The decline on these cold-stored cut cultivars also was up to 24-fold greater than on the cultivar with the lowest decline, and up to 8-fold greater than the mean decline for all 31 cultivars (P < 0.01). Resistance to the hemibiotrophic pathogen causing lettuce bacterial leaf spot, Xanthomonas hortorum pv. vitians, was not indicative of high EcO157 inhibition in this system. High PAL activity, and phenolic and anthocyanin content (PPA); and high PAL and POD activity, were associated with high EcO157 population decline (P < 0.05). One cultivar with high susceptibility to herbivorous insects and phytopathogens, and low levels of defense metabolism nevertheless showed high EcO157 inhibition, suggesting other plant inhibitory characteristics at play. Basal plant immunity and pathways associated with a strong wound response may inform about enteric pathogen survival on minimally processed postharvest lettuce. The related traits identified in this study may serve to breed new genotypes with intrinsically enhanced microbial safety.

Poly-Glutamic Acid Promotes the Growth and the Accumulation of Main Medicinal Components in Salvia miltiorrhiza

Salvia miltiorrhiza Bunge is a traditional medicinal plant in China and poly-glutamic acid (PGA) is a valuable biopolymer. However, it is unclear whether PGA promotes growth and the accumulation of main medicinal components in S. miltiorrhiza. To elucidate this scientific question, the influences of PGA on the growth, physiological characteristics, and accumulation of main medicinal components in S. miltiorrhiza were explored through a pot experiment. The results revealed that PGA significantly promoted basal diameter, plant height, shoot and root biomass, as well as root volume, compared with control. PGA also increased SPAD value, net photosynthetic rate, actual and maximum photochemical efficiency of photosynthetic system II, photochemical quenching, and electronic transfer rate. Meanwhile, PGA increased transpiration rate, stomatal conductance, water use efficiency, leaf relative water content, and the contents of soluble protein, soluble sugar, and proline. Furthermore, PGA increased the activities of antioxidant enzymes and the contents of antioxidants. The above findings imply that PGA facilitated S. miltiorrhiza growth by enhancing photosynthetic performance, water metabolism, and antioxidant capacity. Additionally, PGA significantly improved the yield of rosmarinic acid, salvianolic acid B, dihydrotanshinone, cryptotanshinone, tanshinone I, and tanshinone ⅡA in roots by up-regulating the transcript levels of genes responsible for their biosynthesis. Our findings indicated that PGA promoted S. miltiorrhiza growth and the accumulation of main medicinal components in roots.

Cold priming on pathogen susceptibility in the Arabidopsis eds1 mutant background requires a functional stromal Ascorbate Peroxidase

ABSTRACT 24 h cold exposure (4°C) is sufficient to reduce pathogen susceptibility in Arabidopsis thaliana against the virulent Pseudomonas syringae pv. tomato (Pst) strain even when the infection occurs five days later. This priming effect is independent of the immune regulator Enhanced Disease Susceptibility 1 (EDS1) and can be observed in the immune-compromised eds1–2 null mutant. In contrast, cold priming-reduced Pst susceptibility is strongly impaired in knock-out lines of the stromal and thylakoid ascorbate peroxidases (sAPX/tAPX) highlighting their relevance for abiotic stress-related increased immune resilience. Here, we extended our analysis by generating an eds1 sapx double mutant. eds1 sapx showed eds1-like resistance and susceptibility phenotypes against Pst strains containing the effectors avrRPM1 and avrRPS4. In comparison to eds1–2, susceptibility against the wildtype Pst strain was constitutively enhanced in eds1 sapx. Although a prior cold priming exposure resulted in reduced Pst titers in eds1–2, it did not alter Pst resistance in eds1 sapx. This demonstrates that the genetic sAPX requirement for cold priming of basal plant immunity applies also to an eds1 null mutant background.

Phytophthora palmivora causes root and basal stem rot disease on macaw palm (Acrocomia aculeata) in Brazil

Macaw palm (Acrocomia aculeata Jacq.) is an oleaginous palm native to the American continent. It produces oil and has other important characteristics for the industry. In 2022, a severe disease causing basal stem rot, root rot, and plant mortality in a nursery and the field was detected on macaw palm plants in a farm, in João Pinheiro, Minas Gerais state, Brazil. From the rot symptomatic tissue of affected palms, two Phytophthora isolates were obtained by indirect isolation and were grown on PDA. Based on the morphological characteristics, particularly the coenocytic hyphae and papillate sporangia, the isolates were identified as Phytophthora palmivora. For phylogenetic analyses, the internal transcribed spacer (ITS) regions, β-tubulin gene (TUB), translation elongation factor 1-alpha gene (EF1-α), and two mitochondrial genes: cytochrome c oxidase subunit I (COXI) and cytochrome c oxidase subunit II (COXII), were amplified. Phylogenetic analyses confirmed that it is the species P. palmivora. Fulfillment of the Koch's postulates through pathogenicity test confirmed that P. palmivora was the causal agent of root rot and basal stem rot disease in macaw palm. This is the first report of this pathogen causing disease in macaw palms in Brazil.

Diverse O-methyltransferases catalyze the biosynthesis of floral benzenoids that repel aphids from the flowers of waterlily Nymphaea prolifera.

Nymphaea is a key genus of the ANA grade (Amborellales, Nymphaeales, and Austrobaileyales) of basal flowering plants, which serve as a key model to study the early evolution of floral traits. In this study, we comprehensively investigated the emission, biosynthesis, and biological function of the floral scent in a night-blossoming waterlily Nymphaea prolifera. The headspace volatile collection combined with GC-MS analysis showed that the floral scent of N. prolifera is predominately comprised by methylated benzenoids including anisole, veratrole, guaiacol, and methoxyanisole. Moreover, the emission of these floral benzenoids in N. prolifera exhibited temporal and spatial pattern with circadian rhythm and tissue specificity. By creating and mining transcriptomes of N. prolifera flowers, 12 oxygen methyltransferases (NpOMTs) were functionally identified. By in vitro enzymatic assay, NpOMT3, 6, and 7 could produce anisole and NpOMT5, 7, 9, produce guaiacol, whereas NpOMT3, 6, 9, 11 catalyzed the formation of veratrole. Methoxyanisole was identified as the universal product of all NpOMTs. Expression patterns of NpOMTs provided implication for their roles in the production of the respective benzenoids. Phylogenetic analysis of OMTs suggested a Nymphaea-specific expansion of the OMT family, indicating the evolution of lineage-specific functions. In bioassays, anisole, veratrole, and guaiacol in the floral benzenoids were revealed to play the critical role in repelling waterlily aphids. Overall, this study indicates that the basal flowering plant N. prolifera has evolved a diversity and complexity of OMT genes for the biosynthesis of methylated benzenoids that can repel insects from feeding the flowers. These findings provide new insights into the evolutional mechanism and ecological significance of the floral scent from early-diverged flowering plants.

Somatic Embryogenesis and Plant Regeneration from Stem Explants of Pomegranate

Plant regeneration through somatic embryogenesis provides a solution for maintaining and genetically improving crop or fruit varieties with desirable agronomic traits. For the fruit tree pomegranate (Punica granatum L.), despite some successful applications, the existing somatic embryogenesis protocols are limited by low availability of explants and susceptibility to browning. To address these problems, in this study, we developed an effective system for induction of high-vigor pomegranate somatic embryos derived from stem explants. The usage of stem explants breaks through the difficulty in obtaining material, thus making our system suitable for widespread commercial production. To enhance the performance of our system, we identified the optimal explants, subculture cycles and combination of basal media and plant growth regulators for each step. The results showed that inoculating stem explants onto a Murashige and Skoog (MS) medium supplemented with 1.0 mg/L 6-benzylaminopurine (6-BA) and 1.0 mg/L 1-naphthaleneacetic acid (NAA) achieved the best induction rate and growth status of pomegranate calli (induction rate = ~72%), and MS medium containing 0.5 mg/L 6-BA and 1.0 mg/L NAA was the optimal condition for the induction of embryogenic calli and somatic embryos (induction rate = ~74% and 79%, respectively). The optimal subculture period for embryogenic calli was found to be 30–35 days. Strong roots were then induced in the developed somatic embryo seedlings, which survived and grew well after transplantation to the natural environment, indicating the good vitality of the induced pomegranate somatic embryos. Together, our system provides a solution to mass somatic embryo induction and plant regeneration of pomegranate and lays a foundation for future genetic transformation and bioengineering improvement of pomegranate with favorable agronomic traits.

Deciphering Genetic Variability, Traits Association, Correlation and Path Coefficient in Selected Boro Rice (Oryza sativa L.) Landraces

The study was conducted to evaluate the mean performance, variability along with heritability, correlation coefficient and path coefficients from data collected on 48 Boro rice landraces. Amboro 2 (Golden), Gopal Beshi, Deshi Boro, Kali Boro, Madhabsail, Jagli (Deshi Boro), Pankaich, Joya Boro and Mi-Pajang were found as elite landrace based on the mean performance. High heritability along with genetic advance (GA) and genetic advance in per cent of mean (GAMP) was observed for ligule length, basal leaf length, basal leaf width, culm length, panicle length, test weight, grain length, grain breadth and brown rice length breadth ratio. A positive and significant correlation was observed for basal leaf length, culm length, plant height and yield at both genotypic and phenotypic levels. Basal leaf length and plant height showed a positive direct effect, but culm length showed a negative direct effect at the genotypic level and the situation is just reversed at the phenotypic level for these three traits. However, all these three traits have made the total association positive and significant. Yield had significant (***p&lt;0.001) positive correlations with filled grains number per panicle, days to flowering, days to maturity, grain length, and decorticated grain length breadth ratio. Hence, basal leaf length, culm length, plant height, days to flower and days to maturity are identified as key traits for developing advanced Boro rice breeding lines. The landraces showing a significant amount of variability for yield and its correlated traits can be used for the future breeding program by direct selection based on yield and yield contributing traits.

Influence of Basal Salts, Sucrose and Plant Growth Regulator Levels on Nucellar Embryogenesis and Plantlet Regeneration in Monoembryonic Mango Varieties

Current study described stage-wise protocols for in vitro propagation of commercially important varieties of mango. Induction of somatic embryos (SE) and plantlet regeneration was obtained using nucellar explants of three superior monoembryonic mango vars.‘Saroli’, ‘Langra’, and ‘Chaunsa’ were cultivated in Khairpur, Pakistan. The immature fruits (2.5-4.0 cm long) were surface disinfected using a 30% sodium hypochlorite (NaOCl) solution. Results revealed that significantly highest direct somatic embryogenesis (93%) was obtained in var. ‘Chaunsa’ under full dark on culture medium comprising of 2.0 mg L-1 N6 2-isopentenyl adenine (2iP), 0.5 mg L-1 2,4-dichlorophenoxyacetic acid (2,4-D). Medium consisted of 2iP 4.0 mg L-1, 2,4-D 1.0 mg L-1 induced significantly highest embryogenic callus (91%) using nucellar explants in var.‘Chaunsa’. Significantly highest germination (95%) of SE was achieved in var. ‘Chaunsa’ on the medium comprising microsalts of MS, macrosalts of B5, 2iP 0.1 mg L-1, Kinetin (Kin) 0.5 mg L-1. Highest shoot length (5.1 cm) and root length (4 cm) were obtained in var. ‘Langra’ on the medium consisted of microsalts of MS, macrosalts of B5, 30 g L-1 sucrose, 200 mg L-1 activated charcoal (AC), 0.1 mg L-1 naphthalene acetic acid (NAA), 0.2 mg L-1 benzyl adenine (BA). Stage-wise protocols established for the regeneration of plantlets can be useful for micropropagation of the other mango varieties of the world.

Induction of plant disease resistance by mixed oligosaccharide elicitors prepared from plant cell wall and crustacean shells.

Basal plant immune responses are activated by the recognition of conserved microbe-associated molecular patterns (MAMPs), or breakdown molecules released from the plants after damage by pathogen penetration, so-called damage-associated molecular patterns (DAMPs). While chitin-oligosaccharide (CHOS), a primary component of fungal cell walls, is most known as MAMP, plant cell wall-derived oligosaccharides, cello-oligosaccharides (COS) from cellulose, and xylo-oligosaccharide (XOS) from hemicellulose are representative DAMPs. In this study, elicitor activities of COS prepared from cotton linters, XOS prepared from corn cobs, and chitin-oligosaccharide (CHOS) from crustacean shells were comparatively investigated. In Arabidopsis, COS, XOS, or CHOS treatment triggered typical defense responses such as reactive oxygen species (ROS) production, phosphorylation of MAP kinases, callose deposition, and activation of the defense-related transcription factor WRKY33 promoter. When COS, XOS, and CHOS were used at concentrations with similar activity in inducing ROS production and callose depositions, CHOS was particularly potent in activating the MAPK kinases and WRKY33 promoters. Among the COS and XOS with different degrees of polymerization, cellotriose and xylotetraose showed the highest activity for the activation of WRKY33 promoter. Gene ontology enrichment analysis of RNAseq data revealed that simultaneous treatment of COS, XOS, and CHOS (oligo-mix) effectively activates plant disease resistance. In practice, treatment with the oligo-mix enhanced the resistance of tomato to powdery mildew, but plant growth was not inhibited but rather tended to be promoted, providing evidence that treatment with the oligo-mix has beneficial effects on improving disease resistance in plants, making them a promising class of compounds for practical application.

Tropical insectivorous birds’ predation patterns that promote forest–farmland trophic connectivity for integrated top–down pest biocontrol

Although conversion of natural forest to agriculture can negatively impact biodiversity in many ways, some affected species may respond by dispersing across the forest–farmland eco-zone, thereby facilitating functional connections through food-web interactions beneficial to crop production and forestry. This study examined patterns of Lepidoptera (butterflies and moths), Hemiptera (bugs), and Coleoptera (beetles) herbivory, and insectivorous bird predation within forest-adjacent farms in western Kenya, and how these processes trophically connect the two ecosystems to promote pest biocontrol. Through δ13C and δ15N stable isotope analyses, proportions of maize, farmland legumes and forest trees in pest diets, and pest-prey in bird’s diets were estimated. Birds’ habitat associations and diet specializations’ influence on pest consumption and basal plant carbon levels in birds’ tissues were determined to evaluate birds’ pest-biocontrol potential. Maize was the mostly consumed plant especially by Lepidoptera, but forest trees were peimarily consumed by Coleoptera and Hemiptera. In turn, Lepidoptera were mainly consumed by forest-associated birds, whereas Hemiptera and Coleoptera were mostly consumed by farmland-associated birds. Thus, birds showed cross-habitat pest consumption tendencies, though diet-specialization was unimportant in predicting those tendencies. Muscicapidae (flycatchers and allies); Hirundinidae (swifts and swallows); Motacillidae (pipits and wagtails); and Ploceidae (weavers) birds showed the highest contributory potential for pest biocontrol of Lepidoptera pests, but Estrildidae (manikins and waxbills), Muscicapidae, and Malaconotidae (boubous and gonoleks) birds showed the best potential against Hemiptera and Coleoptera. Furthermore, more maize basal carbon was assimilated by forest-associated compared to farmland-associated birds, whereas most basal carbon from farmland legumes and forest trees were assimilated by farmland birds, suggesting that unlike pest-prey choice, basal plant carbon pathways to avian insectivorous consumers did not strongly mirror birds’ habitat associations. Lepidoptera and Hemiptera were potentially the most significant interhabitat trophic connector arthropods, and for birds, Muscicapidae, Ploceidae, and Estrildidae. These findings show that such functional connectivity may be enhanced through increasing structural cover elements that promote insectivorous birds’ dispersal between farmland and adjacent forests to boost their pest-regulation ecosystem service contribution. The results serve to inform effective management practices by agronomists, foresters, and land-use planners toward promoting landscape-scale-integrated pest management for sustainable agriculture and biodiversity conservation.

A chitin deacetylase PsCDA2 from Puccinia striiformis f. sp. tritici confers disease pathogenicity by suppressing chitin-triggered immunity in wheat.

Plants have the ability to recognize the essential chitin molecule present in the fungal cell wall, which stimulates the immune response. Phytopathogenic fungi have developed various strategies to inhibit the chitin-triggered immune response. Here, we identified a chitin deacetylase of Puccinia striiformis f. sp. tritici (Pst), known as PsCDA2, that was induced during the initial invasion of wheat and acted as an inhibitor of plant cell death. Knockdown of PsCDA2 in wheat enhanced its resistance against Pst, highlighting the significance of PsCDA2 in the host-pathogen interaction. Moreover, PsCDA2 can protect Pst urediniospores from being damaged by host chitinase in vitro. PsCDA2 also suppressed the basal chitin-induced plant immune response, including the accumulation of callose and the expression of defence genes. Overall, our results demonstrate that Pst secretes PsCDA2 as a chitin deacetylase involved in establishing infection and modifying the acetyl group to prevent the breakdown of chitin in the cell wall by host endogenous chitinases. Our research unveils a mechanism by which the fungus suppresses plant immunity, further contributing to the understanding of wheat stripe rust control. This information could have significant implications for the development of suitable strategies for protecting crops against the devastating effects of this disease.

Comparative analysis of mitochondrial genomes of Schisandra repanda and Kadsura japonica.

The family Schisandraceae is a basal angiosperm plant group distributed in East and Southeast Asia and includes many medicinal plant species such as Schisandra chinensis. In this study, mitochondrial genomes (mitogenomes) of two species, Schisandra repanda and Kadsura japonica, in the family were characterized through de novo assembly using sequencing data obtained with Oxford Nanopore and Illumina sequencing technologies. The mitogenomes of S. repanda were assembled into one circular contig (571,107 bp) and four linear contigs (10,898-607,430 bp), with a total of 60 genes: 38 protein-coding genes (PCGs), 19 tRNA genes, and 3 rRNA genes. The mitogenomes of K. japonica were assembled into five circular contigs (211,474-973,503 bp) and three linear contigs (8,010-72,712 bp), with a total of 66 genes: 44 PCGs, 19 tRNA genes, and 3 rRNA genes. The mitogenomes of the two species had complex structural features with high repeat numbers and chloroplast-derived sequences, as observed in other plant mitogenomes. Phylogenetic analysis based on PCGs revealed the taxonomical relationships of S. repanda and K. japonica with other species from Schisandraceae. Finally, molecular markers were developed to distinguish between S. repanda, K. japonica, and S. chinensis on the basis of InDel polymorphisms present in the mitogenomes. The mitogenomes of S. repanda and K. japonica will be valuable resources for molecular and taxonomic studies of plant species that belong to the family Schisandraceae.