Avenacins are antimicrobial triterpene glycosides that are produced by oat (Avena) roots. These compounds confer broadspectrum resistance to soil pathogens. Avenacin A-1, the major avenacin produced by oats, is strongly UV fluorescent and accumulates in root epidermal cells. We previously defined nine loci required for avenacin synthesis, eight of which are clustered. Mutants affected at seven of these (including Saponin-deficient1 [Sad1], the gene for the first committed enzyme in the pathway) have normal root morphology but reduced root fluorescence. In this study, we focus on mutations at the other two loci, Sad3 (also within the gene cluster) and Sad4 (unlinked), which result in stunted root growth, membrane trafficking defects in the root epidermis, and root hair deficiency. While sad3 and sad4 mutants both accumulate the same intermediate, monodeglucosyl avenacin A-1, the effect on avenacin A-1 glucosylation in sad4 mutants is only partial. sad1/sad1 sad3/sad3 and sad1/sad1 sad4/sad4 double mutants have normal root morphology, implying that the accumulation of incompletely glucosylated avenacin A-1 disrupts membrane trafficking and causes degeneration of the epidermis, with consequential effects on root hair formation. Various lines of evidence indicate that these effects are dosage-dependent. The significance of these data for the evolution and maintenance of the avenacin gene cluster is discussed.

Background: Glycosyltransferases (GTs) have important functions in plant secondary metabolism. Results: A gene encoding an N-methylanthranilic acid O-glucosyltransferase forms part of a biosynthetic cluster for the synthesis of acylated defense compounds in oat. Conclusion: This GT synthesizes the activated acyl donor required for triterpene acylation. Significance: These findings open up new opportunities for metabolic engineering for disease control.

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Chiang Rai Province is home to the largest Arabica coffee plantation, accounting for 16% of coffee plantation in Thailand. During the green bean production from coffee cherries, 45% of the coffee pulp is treated as agricultural waste. This study aimed to increase the value of the coffee cherry pulp by using it as an alternative source of pectin. A double extraction process was used to extract pectin: in the first extraction, acid was used to extract the coffee pulp, followed by the second extraction with base. Both acid and base solutions yielded from the extractions were combined prior to the pectin precipitation step. The pectin yield from this double extraction method was 2-fold higher than that yielded from previous methods. Furthermore, to reduce toxicity during the extraction method, we use citric acid to replace hydrochloric and nitric acids. Among three heating conditions during extraction: boiling, autoclave, and microwave, the boiling method gave the highest pectin yield at 15.9%. Unlike the high methoxyl pectin (HMP) yield from citrus, the coffee pectin from the boiling and microwave-assisted methods was categorized as the low methoxyl pectin (LMP). The LMP from coffee cherry can be used as prebiotic supplement or in wound dressing film production. Importantly, producing LMP not only has the potential to reduce post-harvest agricultural waste by 3800 tons per year in Chiang Rai Province but also provides value to agricultural waste and additional income to coffee growers.