Root-exuded specialized metabolites reduce arsenic toxicity in maize. Proceedings of the National Academy of Sciences of the United States of America By releasing specialized metabolites, plants modify their environment. Whether and how specialized metabolites protect plants against toxic levels of trace elements is not well understood. We evaluated whether benzoxazinoids, which are released into the soil by major cereals, can confer protection against arsenic toxicity. Benzoxazinoid-producing maize plants performed better in arsenic-contaminated soils than benzoxazinoid-deficient mutants in the greenhouse and the field. Adding benzoxazinoids to the soil restored the protective effect, and the effect persisted to the next crop generation via positive plant-soil feedback. Arsenate levels in the soil and total arsenic levels in the roots were lower in the presence of benzoxazinoids. Thus, the protective effect of benzoxazinoids is likely soil-mediated and includes changes in soil arsenic speciation and root accumulation. We conclude that exuded specialized metabolites can enhance protection against toxic trace elements via soil-mediated processes and may thereby stabilize crop productivity in polluted agroecosystems. 10.1073/pnas.2314261121

Plant secondary metabolite-dependent plant-soil feedbacks can improve crop yield in the field. eLife Plant secondary metabolites that are released into the rhizosphere alter biotic and abiotic soil properties, which in turn affect the performance of other plants. How this type of plant-soil feedback affects agricultural productivity and food quality in the field in the context of crop rotations is unknown. Here, we assessed the performance, yield and food quality of three winter wheat varieties growing in field plots whose soils had been conditioned by either wild type or benzoxazinoid-deficient maize mutant plants. Following maize cultivation, we detected benzoxazinoid-dependent chemical and microbial fingerprints in the soil. The benzoxazinoid fingerprint was still visible during wheat growth, but the microbial fingerprint was no longer detected. Wheat emergence, tillering, growth, and biomass increased in wild type conditioned soils compared to mutant conditioned soils. Weed cover was similar between soil conditioning treatments, but insect herbivore abundance decreased in benzoxazinoid-conditioned soils. Wheat yield was increased by over 4% without a reduction in grain quality in benzoxazinoid-conditioned soils. This improvement was directly associated with increased germination and tillering. Taken together, our experiments provide evidence that soil conditioning by plant secondary metabolite producing plants can increase yield via plant-soil feedbacks under agronomically realistic conditions. If this phenomenon holds true across different soils and environments, optimizing root exudation chemistry could be a powerful, genetically tractable strategy to enhance crop yields without additional inputs. 10.7554/eLife.84988

IQ domain-containing protein ZmIQD27 modulates water transport in maize. Plant physiology Plant metaxylem vessels provide physical support to promote upright growth and the transport of water and nutrients. A detailed characterization of the molecular network controlling metaxylem development is lacking. However, knowledge of the events that regulate metaxylem development could contribute to the development of germplasm with improved yield. In this paper, we screened an EMS-induced B73 mutant library, which covers 92% of maize (Zea mays) genes, to identify drought-sensitive phenotypes. Three mutants were identified, named iqd27-1, iqd27-2, and iqd27-3, and genetic crosses showed that they were allelic to each other. The causal gene in these 3 mutants encodes the IQ domain-containing protein ZmIQD27. Our study showed that defective metaxylem vessel development likely causes the drought sensitivity and abnormal water transport phenotypes in the iqd27 mutants. ZmIQD27 was expressed in the root meristematic zone where secondary cell wall deposition is initiated, and loss-of-function iqd27 mutants exhibited a microtubular arrangement disorder. We propose that association of functional ZmIQD27 with microtubules is essential for correct targeted deposition of the building blocks for secondary cell wall development in maize. 10.1093/plphys/kiad390

Natural polymorphisms in ZmIRX15A affect water-use efficiency by modulating stomatal density in maize. Plant biotechnology journal Stomatal density (SD) is closely related to crop drought resistance. Understanding the genetic basis for natural variation in SD may facilitate efforts to improve water-use efficiency. Here, we report a genome-wide association study for SD in maize seedlings, which identified 18 genetic variants that could be resolved to seven candidate genes. A 3-bp insertion variant (InDel1089) in the last exon of Zea mays (Zm) IRX15A (Irregular xylem 15A) had the most significant association with SD and modulated the translation of ZmIRX15A mRNA by affecting its secondary structure. Dysfunction of ZmIRX15A increased SD, leading to an increase in the transpiration rate and CO assimilation efficiency. ZmIRX15A encodes a xylan deposition enzyme and its disruption significantly decreased xylan abundance in secondary cell wall composition. Transcriptome analysis revealed a substantial alteration of the expression of genes involved in stomatal complex morphogenesis and drought response in the loss-of-function of ZmIRX15A mutant. Overall, our study provides important genetic insights into the natural variation of leaf SD in maize, and the identified loci or genes can serve as direct targets for enhancing drought resistance in molecular-assisted maize breeding. 10.1111/pbi.14153

Biosynthesis-Based Quantitative Analysis of 151 Secondary Metabolites of Licorice To Differentiate Medicinal Glycyrrhiza Species and Their Hybrids. Song Wei,Qiao Xue,Chen Kuan,Wang Ying,Ji Shuai,Feng Jin,Li Kai,Lin Yan,Ye Min Analytical chemistry Secondary metabolites are usually the bioactive components of medicinal plants. The difference in the secondary metabolisms of closely related plant species and their hybrids has rarely been addressed. In this study, we conducted a holistic secondary metabolomics analysis of three medicinal Glycyrrhiza species (G. uralensis, G. glabra, and G. inflata), which are used as the popular herbal medicine licorice. The Glycyrrhiza species (genotype) for 95 batches of samples were identified by DNA barcodes of the internal transcribed spacer and trnV-ndhC regions, and the chemotypes were revealed by LC/UV- or LC/MS/MS-based quantitative analysis of 151 bioactive secondary metabolites, including 17 flavonoid glycosides, 24 saponins, and 110 free phenolic compounds. These compounds represented key products in the biosynthetic pathways of licorice. For the 76 homozygous samples, the three Glycyrrhiza species showed significant biosynthetic preferences, especially in coumarins, chalcones, isoflavanes, and flavonols. In total, 27 species-specific chemical markers were discovered. The 19 hybrid samples indicated that hybridization could remarkably alter the chemical composition and that the male parent contributed more to the offspring than the female parent did. This is hitherto the largest-scale targeted secondary metabolomics study of medicinal plants and the first report on uniparental inheritance in plant secondary metabolism. The results are valuable for biosynthesis, inheritance, and quality control studies of licorice and other medicinal plants. 10.1021/acs.analchem.6b04919