Identification of novel aphid-killing bacteria to protect plants
Deepa Paliwal, Amanda H Hamilton, Glyn A Barrett, Fabrzio Alberti, Helmut van Emden, Caroline L Monteil, Tim H Mauchine, Ralf Nauen, Carol Wagstaff, Chris Bass, Robert W Jackson
Aphids, including the peach-potato aphid, Myzus persicae, are major insect pests of agriculture and horticulture, and aphid control measures are limited. Recent studies have shown that environmental microbes have varying abilities to kill insects. We screened a range of environmental bacteria isolates for their abilities to kill target aphid species. Tests demonstrated the killing aptitude of these bacteria against six aphid genera (including Myzus persicae). No single bacterial strain was identified that was consistently toxic to insecticide-resistant aphid clones than susceptible clones, suggesting resistance to chemicals is not strongly correlated with bacterial challenge. Our findings provide new insights into aphid susceptibility to bacterial infection with the aim of utilizing bacteria as effective biocontrol agents.
Elucidating connections between the strigolactone biosynthesis pathway, flavonoid production and root system architecture in Arabidopsis thaliana
Bethany L Richmond, Chloe L Coelho, Helen Wilkinson, Joseph McKenna, Pélagie Ratchinski, Maximillian Schwarze, Matthew Frost, Beatriz Lagunas, Miriam L Gifford
Strigolactones (SLs) are the most recently discovered phytohormones, and their roles in root architecture and metabolism are not fully understood. Here, we investigated four MORE AXILLARY GROWTH (MAX) SL mutants in Arabidopsis thaliana, max3-9, max4-1, max1-1 and max2-1, as well as the SL receptor mutant d14-1 and karrikin receptor mutant kai2-2. By characterising max2-1 and max4-1, we found that variation in SL biosynthesis modified multiple metabolic pathways in root tissue, including that of xyloglucan, triterpenoids, fatty acids and flavonoids. The transcription of key flavonoid biosynthetic genes, including TRANSPARENT TESTA4 (TT4) and TRANSPARENT TESTA5 (TT5) was downregulated in max2 roots and seedlings, indicating that the proposed MAX2 regulation of flavonoid biosynthesis has a widespread effect. We found an enrichment of BRI1-EMS-SUPPRESSOR 1 (BES1) targets amongst genes specifically altered in the max2 mutant, reflecting that the regulation of flavonoid biosynthesis likely occurs through the MAX2 degradation of BES1, a key brassinosteroid-related transcription factor. Finally, flavonoid accumulation decreased in max2-1 roots, supporting a role for MAX2 in regulating both SL and flavonoid biosynthesis.
An in-frame deletion mutation in the degron tail of auxin co-receptor IAA2 confers resistance to the herbicide 2,4-D in Sisymbrium orientale
Marcelo R. A. de Figueiredo, Anita Küpper, Jenna M. Malone, Tijana Petrovic, Ana Beatriz T. B. de Figueiredo, Grace Campagnola, Olve B. Peersen, Kasavajhala V.S.K. Prasad, Eric L. Patterson, Anireddy S.N. Reddy, Martin F. Kubeš, Richard Napier, Franck E. Dayan, Christopher Preston, and Todd A. Gaines
The natural auxin indole-3-acetic acid (IAA) is a key regulator of many aspects of plant growth and development. Synthetic auxin herbicides such as 2,4-D mimic the effects of IAA by inducing strong auxinic-signaling responses in plants. To determine the mechanism of 2,4-D resistance in a Sisymbrium orientale (Indian hedge mustard) weed population, we performed a transcriptome analysis of 2,4-D-resistant (R) and -susceptible (S) genotypes that revealed an in-frame 27-nucleotide deletion removing nine amino acids in the degron tail (DT) of the auxin coreceptor Aux/IAA2 (SoIAA2).
Genome Sequencing and Analysis of Trichoderma (Hypocreaceae) Isolates Exhibiting Antagonistic Activity against the Papaya Dieback Pathogen, Erwinia mallotivora
Amin-Asyrat Tamizi, Noriha Mat-Amin, Jack A Weaver, Richard T Olumakaiye, Muhamad Afiq Akbar, Sophie Jin, Hamidun Bunawan and Fabrizio Alberti
Erwinia mallotivora, the causal agent of papaya dieback disease, is a devastating pathogen. A few studies on bacterial species capable of suppressing E. mallotivora have been reported, but the availability of antagonistic fungi remains unknown. In this study, mycelial suspensions from five rhizospheric Trichoderma isolates of Malaysian origin were found to exhibit notable antagonisms against E. mallotivora during co-cultivation. We further characterised three isolates, that showed significant growth inhibition zones on plate-based inhibition assays. Based on these findings, the fungal isolates are proven to be useful as potential biological control agents against E. mallotivora, and the genomic data opens possibilities to further explore the underlying molecular mechanisms behind their antimicrobial activity, with potential synthetic biology applications
Diversity and ecological guild analysis of the oil palm fungal microbiome across root, rhizosphere and soil compartments
The rhizosphere microbiome is a major determinant of plant health, which can interact with the host directly and indirectly to promote or suppress productivity. Currently there is little understanding of the oil palm microbiome and its contribution to plant health and productivity, with existing knowledge based almost entirely on culture dependent studies. We investigated the diversity and composition of the oil palm fungal microbiome in the bulk soil, rhizosphere soil, and roots of 2-, 18-, and 35-year old plantations in Selangor, Malaysia. Many of the fungal sequences showed low similarity to established genera, indicating the presence of substantial novel diversity with significance for plant health within the oil palm microbiome.
Application of ligninolytic bacteria to the enhancement of lignocellulose breakdown and methane production from oil palm empty fruit bunches (OPEFB)
Nurika, Irnia, Shabrina, Eka Nur, Azizah, Nurul, Suhartini, Sri, Bugg, Timothy D. H. and Barker, Guy C.
Efficient pretreatment of lignocellulosic biomass is needed to reduce associated energy costs. Lignin-degrading bacteria (Comamonas testosteroni, Agrobacterium sp., Lysinibacillus sphaericus, and Paenibacillus sp.) were tested as potential pre-treatment methods for oil palm empty fruit bunches (OPEFB) to enhance its methane yield during anaerobic digestion (AD). The highest percentage of lignin breakdown (25.84%) was obtained from OPEFB treated by Lysinibacillus sphaericus, while the highest average specific methane potential (0.042 m3/kg VS) was obtained from treatment with Comamonas testosteroni.