Ethylene-MPK8-ERF.C1-PR module confers resistance against Botrytis cinerea in tomato fruit without compromising ripening.

The plant hormone ethylene plays a critical role in fruit defense against Botrytis cinerea attack, but the underlying mechanisms remain poorly understood. Here, we showed that ethylene response factor SlERF.C1 acts as a key regulator to trigger the ethylene-mediated defense against B. cinerea in tomato fruits without compromising ripening. Knockout of SlERF.C1 increased fruit susceptibility to B. cinerea with no effect on ripening process, while overexpression enhanced resistance. RNA-Seq, transactivation assays, EMSA and ChIP-qPCR results indicated that SlERF.C1 activated the transcription of PR genes by binding to their promoters. Moreover, SlERF.C1 interacted with the mitogen-activated protein kinase SlMPK8 which allowed SlMPK8 to phosphorylate SlERF.C1 at the Ser174 residue and increases its transcriptional activity. Knocking out of SlMPK8 increased fruit susceptibility to B. cinerea, whereas overexpression enhanced resistance without affecting ripening. Furthermore, genetic crosses between SlMPK8-KO and SlERF.C1-OE lines reduced the resistance to B. cinerea attack in SlERF.C1-OE fruits. In addition, B. cinerea infection induced ethylene production which in turn triggered SlMPK8 transcription and enhanced the phosphorylation of SlERF.C1. Overall, our findings reveal the regulatory mechanism of the 'Ethylene-MPK8-ERF.C1-PR' module in resistance against B. cinerea and provide new insight into the manipulation of gray mold disease in fruits.

SlMYB99-mediated auxin and abscisic acid antagonistically regulate ascorbic acids biosynthesis in tomato.

Ascorbic acid (AsA) is a water-soluble antioxidant that plays important roles in plant development and human health. Understanding the regulatory mechanism underlying AsA biosynthesis is imperative to the development of high AsA plants. In this study, we reveal that the auxin response factor SlARF4 transcriptionally inhibits SlMYB99, which subsequently modulates AsA accumulation via transcriptional activation of AsA biosynthesis genes GPP, GLDH, and DHAR. The auxin-dependent transcriptional cascade of SlARF4-SlMYB99-GPP/GLDH/DHAR modulates AsA synthesis, while mitogen-activated protein kinase SlMAPK8 not only phosphorylates SlMYB99, but also activates its transcriptional activity. Both SlMYB99 and SlMYB11 proteins physically interact with each other, thereby synergistically regulating AsA biosynthesis by upregulating the expression of GPP, GLDH, and DHAR genes. Collectively, these results demonstrate that auxin and abscisic acid antagonistically regulate AsA biosynthesis during development and drought tolerance in tomato via the SlMAPK8-SlARF4-SlMYB99/11 module. These findings provide new insights into the mechanism underlying phytohormone regulation of AsA biosynthesis and provide a theoretical basis for the future development of high AsA plants via molecular breeding.

Integrative mRNA and microRNA Analysis Exploring the Inducing Effect and Mechanism of Diallyl Trisulfide (DATS) on Potato against Late Blight.

Potato late blight, caused by Phytophthora infestans, leads to a significant reduction in the yield and value of potato. Biocontrol displays great potential in the suppression of plant diseases. Diallyl trisulfide (DATS) is a well-known natural compound for biocontrol, although there is little information about it against potato late blight. In this study, DATS was found to be able to inhibit the hyphae growth of P. infestans, reduce its pathogenicity on detached potato leaves and tubers, and induce the overall resistance of potato tubers. DATS significantly increases catalase (CAT) activity of potato tubers, and it does not affect the levels of peroxidase (POD), superoxide dismutase (SOD), and malondialdehyde (MDA). The transcriptome datasets show that totals of 607 and 60 significantly differentially expressed genes (DEGs) and miRNAs (DEMs) are detected. Twenty-one negatively regulated miRNA-mRNA interaction pairs are observed in the co-expression regulatory network, which are mainly enriched in metabolic pathways, biosynthesis of secondary metabolites, and starch and sucrose metabolism based on the KEGG pathway. Our observations provide new insight into the role of DATS in biocontrol of potato late blight.

Complete Genome Sequence Data of a Novel Streptomyces sp. Strain A2-16, a Potential Biological Control Agent for Potato Late Blight.

Streptomyces sp. strain A2-16 was recently isolated from potato root zone soil, and it could inhibit the hyphal growth of Phytophthora infestans. The A2-16 genome consisted of one chromosome of 9,765,518 bp and one plasmid of 30,948 bp with GC contents of 70.88% and 68.39%, respectively. A total of 8,518 predicted coding genes, 3 ncRNA,73 tRNA,18 rRNA genes, and 28 secondary metabolite biosynthesis gene clusters were identified. The products of the gene clusters included bioactive polyketides, terpenes, and siderophores, which might contribute to host plants against disease. The average nucleotide identity (ANI) value (82.88-91.41%) among the genome of A2-16 and other Streptomyces species suggested it might not belong to any previously sequenced species in the Streptomyces genus.

Complete Genome Sequence Data of Rare Actinomycetes Strain Saccharothrix texasensis 6-C, a Biological Control Agent for Potato Late Blight.

A rare actinomycetes strain of Saccharothrix texasensis, strain 6-C, has been isolated from the potato rhizosphere and it was shown to act as a biological control agent to potato late blight. It is also the first report on Saccharothrix spp. inhibiting Phytophthora infestans. Here, we present the complete genome data of S. texasensis strain 6-C, assembled by sequencing reads obtained by both PacBio and Illumina technologies with annotation. The final assembled genome length is 9,045,220 bp, without gaps and plasmid, and its GC content is 72.39%. Nine nonribosomal peptides synthetase, five type I polyketide synthase, four terpene, and three lanthipeptide gene clusters were identified in the genome, which would be likely to encode lots of antimicrobial active substances to help host plants against disease. This genome sequence could contribute to investigations of the molecular basis underlying the biocontrol activity of this Saccharothrix strain.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Plant Gravitropism and Signal Conversion under a Stress Environment of Altered Gravity.

Humans have been committed to space exploration and to find the next planet suitable for human survival. The construction of an ecosystem that adapts to the long-term survival of human beings in space stations or other planets would be the first step. The space plant cultivation system is the key component of an ecosystem, which will produce food, fiber, edible oil and oxygen for future space inhabitants. Many plant experiments have been carried out under a stimulated or real environment of altered gravity, including at microgravity (0 g), Moon gravity (0.17 g) and Mars gravity (0.38 g). How plants sense gravity and change under stress environment of altered gravity were summarized in this review. However, many challenges remain regarding human missions to the Moon or Mars. Our group conducted the first plant experiment under real Moon gravity (0.17 g) in 2019. One of the cotton seeds successfully germinated and produced a green seedling, which represents the first green leaf produced by mankind on the Moon.

Combination of rhizosphere bacteria isolated from resistant potato plants for biocontrol of potato late blight.

BACKGROUND: Potato late blight (PLB) caused by Phytophthora infestans is one of the most devastating plant diseases. The heavy use of chemical control agents is at odds with the development of sustainable and environmentally friendly agriculture practices. It is necessary to screen the antagonistic microorganisms of P. infestans and provide a new choice of PLB biocontrol. RESULTS: In vitro, eight bacterial strains (A, B, C, D, E, F, G, H) isolated from the rhizosphere of resistant potato plants had a significant inhibitory effect on the mycelium growth of P. infestans, and the inhibition rate was 35.02-79.20%. These isolates were assigned to Streptomyces, Pseudomonas, Saccharothrix and Nocardiopsis by phylogenetic analysis of 16S rRNA genes. Their physiological and biochemical characteristics suggested that they can produce cellulase and catalase, which may help to inhibit the infection of P. infestans. In vivo, each strain significantly inhibited the infection of P. infestans after individual inoculation into potato tubers, and no strains posed a pathogenic threat to tubers. In the field environment, multibacterial treatment significantly reduced the disease index. Compared with the control, multibacterial and single H treatment significantly increased the microbial species and abundance of the potato rhizosphere and enriched potential beneficial bacteria such as Rhizobiaceae. Meanwhile, multi-bacterial and single H treatment significantly reduced the abundance of Enterobacteriaceae and Bacillaceae. CONCLUSION: Our results provide some valuable native strains from the potato rhizosphere with the ability to inhibit P. infestans in vivo and in vitro, which may be a new option for PLB biocontrol. © 2021 Society of Chemical Industry.

Biocontrol Effect and Possible Mechanism of Food-Borne Sulfide 3-Methylthio-1-Propanol Against Botrytis cinerea in Postharvest Tomato.

Botrytis cinerea is one of the most destructive fungal pathogens causing tremendous losses in fresh fruit or vegetables. 3-Methylthio-1-propanol (3-MP) is a naturally occurring food-borne sulfide, which is mainly used to increase the flavor in food. However, the potential application of 3-MP in the postharvest phase to manage fruit fungal diseases has not been explored. In this study, the antifungal activity of 3-MP against B. cinerea was evaluated, and the possible mechanism involved was explored. In vitro 3-MP treatment could effectively inhibit the mycelial growth, spore germination, and germ tube elongation of B. cinerea. 3-MP also impaired the spore viability and membrane integrity of B. cinerea as well as increased the leakage of nucleic acids, proteins, and malondialdehyde (MDA) in B. cinerea. In vivo 3-MP fumigation treatment inhibited the infection of B. cinerea on tomato fruits. Also, the fruits with 3-MP fumigation treatment exhibited higher antioxidant enzyme activity, lower MDA content, and a significant delay of induction of the expression of most of the stress-related genes when compared to the control group. Moreover, a cytotoxicity evaluation revealed that 3-MP had no toxicity to normal cells in a certain concentration range. Collectively, our research results will provide evidence for the development of food-borne sulfide 3-MP as a fungicide in food and agriculture and will provide an important reference for the formulation of B. cinerea biocontrol strategies.