Hydrogen sulfide (H 2 S) could act as a versatile signaling molecule in delaying fruit ripening and senescence. Ethylene (C 2 H 4 ) also plays a key role in climacteric fruit ripening, but little attention has been given to its interaction with H 2 S in modulating fruit ripening and senescence. To study the role of H 2 S treatment on the fruit quality and nutrient metabolism, tomato fruits at white mature stage were treated with ethylene and ethylene plus H 2 S. By comparing to C 2 H 4 treatment, we found that additional H 2 S significantly delayed the color change of tomato fruit, and maintained higher chlorophyll and lower flavonoids during storage. Moreover, H 2 S could inhibit the activity of protease, maintained higher levels of nutritional-related metabolites, such as anthocyanin, starch, soluble protein, ascorbic acid by comparing to C 2 H 4 treatment. Gene expression analysis showed that additional H 2 S attenuated the expression of beta-amylase encoding gene BAM3, UDP-glycosyltransferase encoding genes, ethylene-responsive transcription factor ERF003 and DOF22. Furthermore, principal component analysis suggested that starch, titratable acids, and ascorbic acid were important factors for affecting the tomato storage quality, and the correlation analysis further showed that H 2 S affected pigments metabolism and the transformation of macromolecular to small molecular metabolites. These results showed that additional H 2 S could maintain the better appearance and nutritional quality than C 2 H 4 treatment alone, and prolong the storage period of post-harvest tomato fruits.

The apple buprestid beetle, Agrilus mali Matsumura (Coleoptera: Buprestidae), can respond to various volatiles, but the underlying mechanism of odorant perception for this insect is poorly understood. Here, we cloned A. mali's odorant-binding proteins 3 (AmalOBP3) and 8 (AmalOBP8) and characterized their expression patterns and binding profiles. Sequence and phylogenetic analyses showed that AmalOBP3 and AmalOBP8 were distributed in the classic and minus-C OBP subfamily, respectively. AmalOBP3 was specifically and abundantly expressed in antennae of both sexes. AmalOBP8 displayed high transcript levels in antennae of both sexes, abdomens of males, and wings of both sexes. Both AmalOBPs exhibited much higher expression in male antennae than in female antennae, suggesting that they could be important in perception of male-specific olfactory cues (e.g., some sex pheromones). Out of the 40 odorant ligands tested, AmalOBP3 and AmalOBP8 bound to 15 and 21 different odorants, respectively, indicating a distinct and selective binding profile for them. Both AmalOBPs seemed to have very strong binding affinity to aliphatic alcohols and aldehydes with 12 to 15 carbon atoms. Alcohols, esters, and terpenoids were more likely to be good ligands for both AmalOBPs than aldehydes and alkanes. Together with its broad expression in different tissues, strong binding with higher numbers of putative ligands for AmalOPB8 means that this protein can have more extensive functional roles in chemosensation of A. mali. Our results provide insights into the molecular basis of chemosensation in A. mali, as well as a basis for developing detection, monitoring, and management tools for this serious pest.

Plant innate immunity is capable of combating diverse and ever evolving pathogens. The plasticity of innate immunity could be boosted by RNA processing. Arabidopsis thaliana CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5 (CPR5), a key negative immune regulator, is a component of the nuclear pore complex. Here we further identified CPR5 as a component of RNA processing complexes. Through genetic screening, we found that RNA splicing activator NineTeen Complex and RNA polyadenylation factor CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR, coordinately function downstream of CPR5 to activate plant immunity. CPR5 and these two regulators forms a complex that is localized in nuclear speckles, an RNA processing organelle. Intriguingly, we found that CPR5 is an RNA-binding protein belonging to the Transformer 2 (Tra2) subfamily of the serine/arginine-rich family. The RNA recognition motif of CPR5 protein binds the Tra2-targeted RNA sequence in vitro and is functionally replaceable by those of Tra2 subfamily proteins. In planta, it binds RNAs of CPR5-regulated alternatively spliced genes (ASGs) identified by RNA-seq. ARGONAUTE 1 (AGO1) is one of the ASGs and, consistent with this, the ago1 mutant suppresses the cpr5 phenotype. These findings reveal that CPR5 is an RNA-binding protein linking RNA processing with plant immunity.

Plant invasions can alter the behaviour and performance of native herbivorous insects because the insects are evolutionarily naïve to the novel plants. An ecological trap results when native insects prefer invasive plants over their native hosts but suffer reduced fitness on the invaders. Although such traps are predicted to occur frequently, given the prevalence of invasive plants, empirical support for ecological traps and their underlying mechanisms remains sparse. We examined the potential for the invasive plant Spartina alterniflora to act as an ecological trap for the native moth Laelia coenosa, which previously fed mainly on the indigenous plant Phragmites australis in a Chinese saltmarsh. We surveyed Laelia egg densities on Spartina and Phragmites in the field, and determined adult oviposition preference and offspring development on the two plant species. To investigate the causes of adult preference and offspring performance patterns, we compared resource abundance in the field, plant‐odour attractiveness and leaf nutritional and defensive traits between Spartina and Phragmites. We found that Laelia egg density and female preference for ovipositing were higher on Spartina than Phragmites. However, performance of offspring was poorer on Spartina than Phragmites. Spartina dominated a larger area and had greater leaf biomass than Phragmites in the field, and volatile odours released by Spartina were more attractive to Laelia females than those released by Phragmites. Although leaf C, C:P ratio and terpenoid content did not differ significantly between the two plant species, Spartina leaves were tougher and more waxy, had lower N and had higher concentrations of alkaloids and phenolics than Phragmites leaves. Synthesis. Our data suggest that invasive Spartina can create an ecological trap for the native insect Laelia. This trap appears to result from environmental cues (resource availability and leaf odours) that attract the herbivore to the plant, but do not reliably predict the dietary qualities (nutrition and defences) that negatively affect herbivore offspring performance. These findings reveal an important negative effect of plant invasions on resident herbivores and highlight the roles of resource availability and plant traits at different life stages of the insect.

No abstract

No abstract

The Arabidopsis trichome is a polyploid epidermal cell resulting from multiple rounds of endocycles. The CYCLIN‐DEPENDENT KINASE INHIBITOR (CKI) family proteins are core cell cycle regulators that promote the endocycle. CONSTITUTIVE EXPRESSION OF PR GENES 5 (CPR5) is a plant‐specific nucleoporin. It has been found that two Arabidopsis CKI, SIAMESE (SIM) and SIAMESE‐RELATED 1 (SMR1), function downstream of CPR5 to activate plant effector‐triggered cell death. The sim smr1 double mutants form multicellular and clustered trichomes, while the cpr5 mutants produce dead and branchless trichomes. This study explored roles of the CPR5‐CKI signalling pathway in trichome cell cycle transition. To examine the underlying mechanism of how cell cycle transition is regulated in plant trichomes, Trypan blue staining, flow cytometry, scanning electron microscopy (SEM) and nuclear DNA measurement were conducted. The native promoter‐driven CKI and GUS fusion reporter showed that both SIM and SMR1 proteins were preferentially expressed in trichomes. The cpr5‐induced dead and branchless trichomes were fully suppressed by the sim smr1 double mutant, suggesting that SIM and SMR1 function downstream of CPR5 in trichome development. Flow cytometry analysis showed that as compared to the number of 2C (C = DNA content in a haploid nucleus) cells, the number of 4C cells significantly increased, whereas that of polyploidy cells (8C and 16C) dramatically decreased in the cpr5 mutant. The elevated 4C/2C ratio in the cpr5 mutant is consistent with de‐repression of pro‐endocycle regulators SIM and SMR1. The polyploidy cells (8C and 16C) may be selectively targeted to cell death, which is therefore attributed to the branchless trichomes in the cpr5 mutant. Nuclear DNA content analysis demonstrated that the nuclear DNA content of trichomes in the cpr5 sim mutant was significantly higher than in the sim mutant, indicating that CPR5 is a negative endocycle regulator in trichomes. This study reveals that the CPR5‐CKI signalling pathway controls trichome cell cycle transition and excessive endocycles are required for cell death in plant trichomes.

Aspergillus niger is a common pathogenic fungus causing postharvest rot of fruit and vegetable, whereas the knowledge on virulence factors is very limited. Superoxide dismutase [SOD (EC 1.15.1.10)] is an important metal enzyme in fungal defense against oxidative damage. Thus, we try to study whether Cu/Zn-SOD is a virulence factor in A. niger. Cu/Zn-SOD encoding gene sodC was deleted in A. niger [MA70.15 (wild type)] by homologous recombination. The deletion of sodC led to decreased SOD activity in A. niger, suggesting that sodC did contribute to full enzyme activity. ΔsodC strain showed normal mycelia growth and sporulation compared with wild type. However, sodC deletion markedly increased the cell’s sensitivity to intracellular superoxide anion generator menadione. Besides, spore germination under menadione and H2O2 stresses were significantly retarded in ΔsodC mutant compared with wild type. Further results showed that sodC deletion induced higher superoxide anion production and higher content of H2O2 and malondialdehyde (MDA) compared with wild type, supporting the role of SOD in metabolism of reactive oxygen species (ROS). Furthermore, ΔsodC mutant had a reduced virulence on chinese white pear (Pyrus bretschneideri) as lesion development by ΔsodC was significantly less than wild type. The determination of superoxide anion, H2O2, and MDA in A. niger-infected pear showed that chinese white pear infected with ΔsodC accumulated less superoxide anion, H2O2, and MDA compared with that of wild type A. niger, implying that ΔsodC induced an attenuated response in chinese white pear during fruit–pathogen interaction. Our results indicate that sodC gene contributes to the full virulence of A. niger during infection on fruit. Aspergillus niger is one of the most common species found in fungal communities. It is an important fermentation industrial strain and is also known to cause the most severe symptoms in fruit during long-term storage (Pel et al., 2007). Meanwhile, plants activate their signaling pathways to trigger defense responses to limit pathogen expansion. One of the earliest host responses after pathogen attack is oxidative burst, during which large quantities of ROS are generated by different host enzyme systems, such as glucose oxidase (Govrin and Levine, 2000). ROS such as singlet oxygen, superoxide anion, hydroxyl (OH−), and H2O2 are released to hinder the advance of pathogens (Gara et al., 2003). ROS can react with and damage cellular molecules, such as DNA, protein, and lipids, which will limit fungal propagation in the host plant (Apel and Hirt, 2004).