Insect-induced daidzein, formononetin and their conjugates in soybean leaves.

In response to attack by bacterial pathogens, soybean (Gylcine max) leaves accumulate isoflavone aglucones, isoflavone glucosides, and glyceollins. In contrast to pathogens, the dynamics of related insect-inducible metabolites in soybean leaves remain poorly understood. In this study, we analyzed the biochemical responses of soybean leaves to Spodoptera litura (Lepidoptera: Noctuidae) herbivory and also S. litura gut contents, which contain oral secretion elicitors. Following S. litura herbivory, soybean leaves displayed an induced accumulation of the flavone and isoflavone aglycones 4',7-dihyroxyflavone, daidzein, and formononetin, and also the isoflavone glucoside daidzin. Interestingly, foliar application of S. litura oral secretions also elicited the accumulation of isoflavone aglycones (daidzein and formononetin), isoflavone 7-O-glucosides (daidzin, ononin), and isoflavone 7-O-(6'-O-malonyl-β-glucosides) (malonyldaidzin, malonylononin). Consistent with the up-regulation of the isoflavonoid biosynthetic pathway, folair phenylalanine levels also increased following oral secretion treatment. To establish that these metabolitic changes were the result of de novo biosynthesis, we demonstrated that labeled (13C9) phenylalanine was incorporated into the isoflavone aglucones. These results are consistent with the presence of soybean defense elicitors in S. litura oral secretions. We demonstrate that isoflavone aglycones and isoflavone conjugates are induced in soybean leaves, not only by pathogens as previously demonstrated, but also by foliar insect herbivory

Evaluation of antixenosis in soybean against <i>Spodoptera litura</i> by dual-choice assay aided by a statistical analysis model: Discovery of a novel antixenosis in Peking

The method for evaluating soybean (Glycine max) antixenosis against the common cutworm (Spodoptera litura) was developed based on a dual-choice assay aided by a statistical analysis model. This model was constructed from the results of a dual-choice assay in which Enrei, a soybean cultivar susceptible to S. litura, was used as both a standard and a test leaf disc for 2nd–5th instar larvae. The statistical criterion created by this model enabled the evaluation of the presence of antixenosis. This method was applied to four soybean varieties, including Tamahomare (susceptible), Himeshirazu (resistant), IAC100 (resistant), and Peking (unknown), as well as Enrei. Subsequently, the degrees of antixenosis were also compared by F-test, followed by maximum likelihood estimation (MLE). According to the results, the antixenosis of Tamahomare, Himeshirazu, and IAC100 was statistically reevaluated and Peking exhibited a novel antixenosis, which was stronger for 3rd–5th instar larvae than for 2nd instar

Methanol bioeconomy: promotion of rice crop yield in paddy fields with microbial cells prepared from natural gas‐derived C 1 compound

微生物やその細胞壁成分の葉面散布による酒米の増収に成功 --メタノールを原料に生産した微生物製剤を出穂後1度の散布で--. 京都大学プレスリリース. 2020-12-11.Methylotrophs, which can utilize methanol as a sole carbon source, are promising microorganisms to be exploited in a methanol‐based bioeconomy, in which a variety of useful compounds are biotechnologically produced from natural gas‐derived methanol. Pink‐pigmented facultative methylotrophs (PPFMs) are common plant phyllospheric bacteria and are known to enhance seedling growth and total biomass of various plants. However, improvement of crop yield by inoculation of PPFMs at the field level has not been well investigated. We herein describe improvement of crop yield of several rice cultivars by foliar spraying of PPFMs. After selection of PPFM strains and rice cultivars by the in vitro seedling growth test, we further conducted paddy field experiments. The crop yield of the sake‐brewing rice Oryza sativa cultivar Hakutsurunishiki was reproducibly improved in a commercial paddy field for over a 5‐year period. A one‐time foliar spray of PPFM cells (living or killed) or a cell wall polysaccharide fraction, after the heading date, acted in the phyllosphere and effectively improved crop yield. Our results show that the established process with PPFMs is feasible for improvement of food production in the methanol bioeconomy

Early embryogenesis-specific expression of the rice transposon Ping enhances amplification of the MITE mPing.

Miniature inverted-repeat transposable elements (MITEs) are numerically predominant transposable elements in the rice genome, and their activities have influenced the evolution of genes. Very little is known about how MITEs can rapidly amplify to thousands in the genome. The rice MITE mPing is quiescent in most cultivars under natural growth conditions, although it is activated by various stresses, such as tissue culture, gamma-ray irradiation, and high hydrostatic pressure. Exceptionally in the temperate japonica rice strain EG4 (cultivar Gimbozu), mPing has reached over 1000 copies in the genome, and is amplifying owing to its active transposition even under natural growth conditions. Being the only active MITE, mPing in EG4 is an appropriate material to study how MITEs amplify in the genome. Here, we provide important findings regarding the transposition and amplification of mPing in EG4. Transposon display of mPing using various tissues of a single EG4 plant revealed that most de novo mPing insertions arise in embryogenesis during the period from 3 to 5 days after pollination (DAP), and a large majority of these insertions are transmissible to the next generation. Locus-specific PCR showed that mPing excisions and insertions arose at the same time (3 to 5 DAP). Moreover, expression analysis and in situ hybridization analysis revealed that Ping, an autonomous partner for mPing, was markedly up-regulated in the 3 DAP embryo of EG4, whereas such up-regulation of Ping was not observed in the mPing-inactive cultivar Nipponbare. These results demonstrate that the early embryogenesis-specific expression of Ping is responsible for the successful amplification of mPing in EG4. This study helps not only to elucidate the whole mechanism of mPing amplification but also to further understand the contribution of MITEs to genome evolution

QTLs underlying the genetic interrelationship between efficient compatibility of <i>Bradyrhizobium</i> strains with soybean and genistein secretion by soybean roots

<div><p>Soybean plants establish symbiotic relationships with soil rhizobia which form nodules on the plant roots. Nodule formation starts when the plant roots exudate isoflavonoids that induce <i>nod</i> gene expression of a specific <i>Bradyrhizobium</i>. We examined the specific indigenous rhizobia that form nodules with the soybean cultivars Peking and Tamahomare in different soils. PCR-RFLP analysis targeted to the 16S-23S rRNA gene internal transcribed spacer (ITS) region of the bacterial type of each root nodule showed that <i>Bradyrhizobium japonicum</i> (USDA110-type) and <i>Bradyrhizobium elkanii</i> (USDA94-type) had high compatibility with the Tamahomare and Peking cultivars, respectively. We grew 93 recombinant inbred lines (RIL) of soybean seeds derived from the cross between Peking and Tamahomare in three different field soils and identified the indigenous rhizobia nodulating each line using the same PCR-RFLP analysis. QTL analysis identified one QTL region in chromosome-18 with a highly significant additive effect that controls compatibility with both <i>B</i>. <i>japonicum</i> USDA110 and <i>B</i>. <i>elkanii</i> USDA94. We also measured the amount of daidzein and genistein secretion from roots of the 93 RILs by HPLC analysis. QTL analysis showed one QTL region in chromosome-18 controlling genistein secretion from roots and coinciding with that regulating compatibility of specific indigenous rhizobia with soybean. The amount of genistein may be a major regulatory factor in soybean-rhizobium compatibility.</p></div

Tracking the genome-wide outcomes of a transposable element burst over decades of amplification

To understand the success strategies of transposable elements (TEs) that attain high copy numbers, we analyzed two pairs of rice (Oryza sativa) strains, EG4/HEG4 and A119/A123, undergoing decades of rapid amplification (bursts) of the class 2 autonomous Ping element and the nonautonomous miniature inverted repeat transposable element (MITE) mPing. Comparative analyses of whole-genome sequences of the two strain pairs validated that each pair has been maintained for decades as inbreds since divergence from their respective last common ancestor. Strains EG4 and HEG4 differ by fewer than 160 SNPs and a total of 264 new mPing insertions. Similarly, strains A119 and A123 exhibited about half as many SNPs (277) as new mPing insertions (518). Examination of all other potentially active TEs in these genomes revealed only a single new insertion out of ∼40, 000 loci surveyed. The virtual absence of any new TE insertions in these strains outside the mPing bursts demonstrates that the Ping/mPing family gradually attains high copy numbers by maintaining activity and evading host detection for dozens of generations. Evasion is possible because host recognition of mPing sequences appears to have no impact on initiation or maintenance of the burst. Ping is actively transcribed, and both Ping and mPing can transpose despite methylation of terminal sequences. This finding suggests that an important feature of MITE success is that host recognition does not lead to the silencing of the source of transposase

Identification of β-phenylalanine as a non-protein amino acid in cultivated rice, Oryza sativa

Non-protein amino acids, often analogs of the standard 20 protein amino acids, have been discovered in many plant species. Recent research with cultivated rice (Oryza sativa) identified (3R)-β-tyrosine, as well as a tyrosine amino mutase that synthesizes (3R)-β-tyrosine from the protein amino acid (2S)-α-tyrosine. Gas chromatography-mass spectrometry (GC-MS) assays and comparison to an authentic standard showed that β-phenylalanine is also a relatively abundant non-protein amino acid in rice leaves and that its biosynthesis occurs independently from that of β-tyrosine