The importance of thiamine (vitamin B1) in plant health: From crop yield to biofortification

Conferring thermotolerant phenotype to wild-type Yarrowia lipolytica improves cell growth and erythritol production

In microbial engineering, heat stress is an important environmental factor modulating cell growth, metabolic flux distribution and the synthesis of target products. Yarrowia lipolytica, as a GARS (generally recognized as safe) nonconventional yeast, has been widely used in the food industry, especially as the host of erythritol production. Biomanufacturing economics is limited by the high operational cost of cooling energy in large-scale fermentation. It is of great significance to select thermotolerant Y. lipolytica to reduce the cooling cost and elucidate the heat-resistant mechanism at molecular level. For this purpose, we performed adaptive evolution and obtained a thermotolerant strain named Y. lipolytica BBE-18. Transcriptome analysis allows us to identify four genes in thiamine metabolism pathway that are responsible for the complicated thermotolerant phenotype. The heat-resistant phenotype was validated with the model strain Y. lipolytica Po1f by overexpression of single and combined genes. Then, conferring the thermotolerant phenotype to the wild-type Y. lipolytica BBE-17 enable the strain to produce three-times more erythritol of the control strain with 3°C higher than optimal cultivation temperature. To our knowledge, this is the first report on engineering heat-resistant phenotype to improve the erythritol production in Y. lipolytica. However, due to the increase of culture temperature, a large amount of adenosine triphosphate is consumed to ensure the life activities of Y. lipolytica which limits the potential of cell synthetic products to a certain extent. Even so, this study provides a reference for Y. lipolytica to produce other products under high temperature.

Of clocks and coenzymes in plants: intimately connected cycles guiding central metabolism?

Plant fitness is a measure of the capacity of a plant to survive and reproduce in its particular environment. It is inherently dependent on plant health. Molecular timekeepers like the circadian clock enhance fitness due to their ability to coordinate biochemical and physiological processes with the environment on a daily basis. Central metabolism underlies these events and it is well established that diel metabolite adjustments are intimately and reciprocally associated with the genetically encoded clock. Thus, metabolic pathway activities are time-of-day regulated. Metabolite rhythms are driven by enzymes, a major proportion of which rely on organic coenzymes to facilitate catalysis. The B vitamin complex is the key provider of coenzymes in all organisms. Emerging evidence suggests that B vitamin levels themselves undergo daily oscillations in animals but has not been studied in any depth in plants. Moreover, it is rarely considered that daily rhythmicity in coenzyme levels may dictate enzyme activity levels and therefore metabolite levels. Here we put forward the proposal that B-vitamin-derived coenzyme rhythmicity is intertwined with metabolic and clock derived rhythmicity to achieve a tripartite homeostasis integrated into plant fitness.

Characterization of near-isogenic lines confirmed QTL and revealed candidate genes for plant height and yield-related traits in common wheat

Plant height (PH) is closely associated with yield-related traits and environmental adaptation. Seven pairs of near-isogenic lines (NILs) targeting four QTL on 3AL, 4BL, 4AS, and 7AL wheat chromosome arms were assessed for PH and four yield-related traits including yield per plant (Y/P), grain number per spike (G/S), thousand kernel weight (TKW), and biomass per plant (B/P). Significant differences were observed in the NIL pairs for the measured traits. NIL pairs targeting the 3AL QTL differed significantly in PH, G/S, and TKW; NILs targeting the 4BL QTL differed significantly in PH, Y/P, and B/P; NIL pairs targeting the 4AS QTL differed significantly in all the traits; and NIL pairs targeting the 7AL QTL differed significantly in PH. A 90 K SNP genotyping assay of the NILs detected nineteen SNPs associated with fourteen functional genes. Among them, eight candidate genes are related to Rht proteins, four genes are related to hormone pathways and two genes are related to carbohydrate synthesis and transport. By searching the interval marker physical positions, it was found that the four targeted QTL in this study overlapped with eight previously reported QTL for PH, TKW, biomass, and yield. Correlation analysis revealed that PH significantly and positively correlated with B/P and G/S. The SNP and candidate gene information is potentially useful for marker-assisted selection in breeding programs, and the four targeted QTL are proved to be critical genomic regions controlling the investigated agronomic traits, which can be further fine mapped to identify the underlying genes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-020-01196-8.

Bacterial inoculation positively affects the quality and quantity of flax under deficit irrigation regimes

AIM

The present research was conducted to investigate the effect of plant growth-promoting rhizobacteria (PGPR) and deficit irrigation on quality and quantity of flax under field and pot conditions to determine bacterial efficiency and to decrease water deficit effects.

METHODS AND RESULTS

Initially, in vitro experiments were performed to determine the growth-promoting characteristics of bacteria. Then in the field, the effects of bacterial inoculation (control, Azotobacter chroococcum, Azospirillum lipoferum, Bacillus amyloliquefaciens, Bacillus sp. strain1 and Pseudomonas putida) on flax traits were evaluated at different irrigation levels (100, 75 and 50% crop water requirement). Bacterial treatments in the pot experiment were selected based on the field experiment results. The irrigation regimes in the pot and field experiments were the same and bacterial treatments included single, doublet and triplet applications of the bacteria. All the bacterial strains could solubilize phosphate, produce ammonia (except for Bacillus sp. strain1), indole acetic acid and siderophore (except P. putida). Field results indicated that the bacteria significantly mitigated the effects of water deficit. Compared with control plants, bacterial treatments increased the oil, linolenic acid, protein and sulphur content; the number of shoots and capsules; and the harvest index in the flax plants. Pot experimental results revealed that the combined inoculations were more effective than single inoculum treatments.

CONCLUSIONS

Bacterial inoculation alleviates deficit irrigation effects in flax plants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The effectiveness of applying A. chroococcum, B. amyloliquefaciens and Bacillus sp. strain1 was confirmed, especially as a combination to protect flax against water deficit and to improve its nutritional quality and growth.

Plants in the real world: An introduction to the JBC Reviews thematic series

The deep relationship between plants and humans predates civilization, and our reliance on plants as sources of food, feed, fiber, fuels, and pharmaceuticals continues to increase. Understanding how plants grow and overcome challenges to their survival is critical for using these organisms to meet current and future demands for food and other plant-derived materials. This thematic review series on "plants in the real world" presents a set of eight reviews that highlight advances in understanding plant health, including the role of thiamine (vitamin B₁), iron, and the plant immune system; how plants use ethylene and ubiquitin systems to control growth and development; and how new gene-editing approaches, the redesign of plant cell walls, and deciphering herbicide resistance evolution can lead to the next generation of crops.