Methiozolin is a new herbicide for control of annual bluegrass (Poa annua L.) in several warm and cool season turfgrasses with an unknown mechanism of action (MOA). In the literature, methiozolin was proposed to be a pigment inhibitor via inhibition of tyrosine aminotransferases (TATs) or a cellulose biosynthesis inhibitor (CBI). Here, exploratory research was conducted to characterize the herbicide symptomology and MOA of methiozolin. Arabidopsis (Arabidopsis thaliana L.) and P. annua exhibited a similar level of susceptibility to methiozolin and arrestment of meristematic growth was the most characteristic symptomology. For example, methiozolin inhibited Arabidopsis root growth (GR50 8 nM), shoot emergence (GR80 ~50 nM), and at rates greater than 500 nM apical meristem growth was completely arrested. We concluded that methiozolin was neither a TAT nor a CBI inhibitor. Methiozolin had a minor effect on chlorophyll and alpha-tocopherol content in treated seedlings (< 500 nM) and supplements in the proposed TAT pathway could not lessen phytotoxicity. Examination of microscopy root images revealed methiozolin treated (100 nM) and untreated seedlings had similar root cell lengths. Thus, methiozolin inhibits cell proliferation and not elongation from meristematic tissue. Subsequently, we suspected methiozolin was an inhibitor of the mevalonic acid (MVA) pathway because its herbicidal symptomologies were nearly indistinguishable from those caused by lovastatin. However, methiozolin did not inhibit phytosterol production and MVA pathway metabolites did not rescue treated seedlings. Further experiments showed that methiozolin produced a very similar physiological profile across a number of assays as cinmethylin, a known inhibitor of fatty acid synthesis through inhibition of thioesterases (FATs). Experiments with Lemna showed that methiozolin also reduced fatty acid content in Lemna with a profile similar, but not identical, to cinmethylin. However, there was no difference in fatty acid content between treated (1 µM) and untreated Arabidopsis seedlings. Methiozolin also bound to both Arabidopsis and Lemna FATs in vitro. Modeling suggested that methiozolin and cinmethylin have comparable and overlapping binding sites to FAT. While there was a discrepancy in the effect of methiozolin on fatty acid content between Lemna and Arabidopsis, the overall evidence indicates that methiozolin is a FAT inhibitor and acts in a similar manner as cinmethylin.
Increasing the production of plant oils such as soybean oil as a renewable resource for food and fuel is valuable. Successful breeding for higher oil levels in soybean, however, usually results in reduced protein, a second valuable seed component. This study shows that by manipulating a highly active acyl-CoA:diacylglycerol acyltransferase (DGAT) the hydrocarbon flux to oil in oilseeds can be increased without reducing the protein component. Compared to other plant DGATs, a DGAT from Vernonia galamensis (VgDGAT1A) produces much higher oil synthesis and accumulation activity in yeast, insect cells, and soybean. Soybean lines expressing VgDGAT1A show a 4% increase in oil content without reductions in seed protein contents or yield per unit land area. Incorporation of this trait into 50% of soybeans worldwide could result in an increase of 850 million kg oil/year without new land use or inputs and be worth ∼U.S.$1 billion/year at 2012 production and market prices.
Soybean (Glycine max L.) seed is a major source of protein, oil, carbohydrates and other nutrients that are important for human and animal nutrition. Producers have considered applying nitrogen (N) fertilizer to soybean crop to maximize seed yield; however, its effect on seed composition is not well understood. The objective of this two-year (2015 and 2016) study was to evaluate the effects of N fertilizer sources and application rates (45, 90, 135 and 179 kg N ha −1 ) on soybean seed composition on two soil textures (clay and silt-loam) in Mississippi. The three fertilizer sources included in this study were urea with N-(n butyl) thiophosphoric triamide (Urea+NBPT), polymer-coated urea (PCU), and ammonium sulfate (AMS). Nitrogen application at 179 kg ha −1 on clay soil reduced seed protein by 1.05% compared to unfertilized soybeans in 2016. However, N application at 179 kg ha −1 increased oil content by 0.7% on clay soil compared to the unfertilized soybeans only in 2016. Nitrogen applications reduced stachyose content on both soil textures in 2015. The fatty acids showed variable response to N applications. Since, seed quality is not a trait from which growers receive an economic incentive, they are unlikely to adopt this practice for standard soybean production.
Chia (Salvia hispanica) is an ancient crop that has experienced an agricultural resurgence in recent decades owing to the high omega 3 fatty acid (ω‐3) content of the seeds and good production potential. Analysis of 563 lots of chia grown in Kentucky and 10 lots from Arizona, Australia, Mexico, and Peru was performed. All of these lots were assessed for fatty acid, oil, and protein content, while a subset of 120 samples were assessed for amino acids, fiber, minerals, and trace elements. The mean oil content was 31.3%, ranging from 21.4% to 35.3%. The protein content averaged 22.8%, ranging from 18.2% to 28.2%, and the ω‐3 FA α‐linolenic acid (ALA) averaged 61.3%, ranging from 33.9% to 69.9%. Using these seed lots, nondestructive near‐infrared spectroscopy (NIRS) calibrations were developed for whole and ground seed oil, protein, moisture, and the six major fatty acids. The R2 and SE of cross‐validation (SECV) values for oil were 0.78 and 0.95, respectively, while those for protein were 0.75 and 1.05, respectively. The NIRS calibrations for fatty acid had R2 and SECV greater than 0.6 and less than 10% of actual values for all major fatty acids, respectively. An R2 of 0.99 was established for moisture content of whole seeds within the range of 3–10% moisture content. The precision and accuracy of these calibrations is adequate for use by breeders, growers, and food quality experts to quantitatively assess these major constituents without the need for costly and time‐consuming chemical analysis.
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