Insect pests cause significant global agricultural damage and lead to major financial and environmental costs. Crops contain intrinsic defenses to protect themselves from such pests, including a wide array of specialized secondary metabolite-based defense chemicals. These chemicals can be induced upon attack (phytoalexins) or are constitutive (phytoanticipins), and can have a direct impact on the pests or be used indirectly to attract their natural enemies. They form part of a global arms race between the crops and their insect pests, with the insects developing methods of suppression, avoidance, detoxification, or even capture of their hosts defensive chemicals. Harnessing and optimizing the chemical defense capabilities of crops has the potential to aid in the continuing struggle to enhance or improve agricultural pest management. Such strategies include breeding for the restoration of defense chemicals from ancestral varieties, or cross-species transfer of defense metabolite production.

No abstract

Myo ‐inositol oxygenase (MIOX) is the first enzyme in the inositol route to ascorbate (L‐ascorbic acid, AsA, vitamin C). We have previously shown that Arabidopsis plants constitutively expressing MIOX have elevated foliar AsA content and displayed enhanced growth rate, biomass accumulation, and increased tolerance to multiple abiotic stresses. In this work, we used a combination of transcriptomics, chromatography, microscopy, and physiological measurements to gain a deeper understanding of the underlying mechanisms mediating the phenotype of the At MIOX4 line. Transcriptomic analysis revealed increased expression of genes involved in auxin synthesis, hydrolysis, transport, and metabolism, which are supported by elevated auxin levels both in vitro and in vivo, and confirmed by assays demonstrating their effect on epidermal cell elongation in the At MIOX4 over‐expressers. Additionally, we detected up‐regulation of transcripts involved in photosynthesis and this was validated by increased efficiency of the photosystem II and proton motive force. We also found increased expression of amylase leading to higher intracellular glucose levels. Multiple gene families conferring plants tolerance/expressed in response to cold, water limitation, and heat stresses were found to be elevated in the At MIOX4 line. Interestingly, the high AsA plants also displayed up‐regulation of transcripts and hormones involved in defense including jasmonates, defensin, glucosinolates, and transcription factors that are known to be important for biotic stress tolerance. These results overall indicate that elevated levels of auxin and glucose, and enhanced photosynthetic efficiency in combination with up‐regulation of abiotic stresses response genes underly the higher growth rate and abiotic stresses tolerance phenotype of the At MIOX4 over‐expressers.

No abstract

Galphimia glauca is a plant that is endemic to Mexico and has been commonly used since pre-Hispanic times to treat various illnesses, including central nervous system disorders and inflammation. The first studies investigating a natural population of G . glauca in Mexico showed that the plant has anxiolytic and sedative activities in mice and humans. The plant’s bioactive compounds were isolated and identified, and they belong to a family of nor -secofriedelanes called galphimines. The integration of DNA barcoding and thin-layer chromatography analysis was performed to clarify whether the botanical classification of the populations in the study, which were collected in different regions of Mexico, as G . glauca was correct or if the populations consist of more than one species of the genus Galphimia . We employed six DNA barcodes ( matK , rbcL , rpoC1 , psbA-trnH , ITS1 and ITS2 ) that were analyzed individually and in combination and then compared each other, to indicate differences among the studied populations. In the phylogenetic analysis, ITS1 and ITS2 markers as well as the combination of all DNA regions were the most efficient for discriminating the population studied. The thin-layer chromatography analysis exhibited four principal chemical profiles, one of which corresponded to the populations that produced galphimines. DNA barcoding was consistent and enabled us to differentiate the populations that produce galphimines from those that do not. The results of this investigation suggest that the studied populations belong to at least four different species of the genus Galphimia . The phylogenetic analysis and the thin-layer chromatography chemical profiles were convenient tools for establishing a strong relationship between the genotype and phenotype of the studied populations and could be used for quality control purposes to prepare herbal medicines from plants of the genus Galphimia .

Premise AVP1 (H+‐pyrophosphatase) and MIOX4 (myo‐inositol oxygenase) are genes that, when overexpressed individually, enhance the growth and abiotic stress tolerance of Arabidopsis thaliana plants. We propose that pyramiding AVP1 and MIOX4 genes will further improve stress tolerance under water‐limited and salt‐stress conditions. Methods MIOX4 and AVP1 reciprocal crosses were developed and phenomic approaches used to investigate the possible synergy between these genes. Results Under normal and stress conditions, the crosses had higher foliar ascorbate content than the wild‐type and parental lines. Under water‐limited conditions, the crosses also displayed an enhanced growth rate and biomass compared with the control. The observed increases in photosystem II efficiency, linear electron flow, and relative chlorophyll content may have contributed to this observed phenotype. Additionally, the crosses retained more water than the controls when subjected to salt stress. Higher seed yields were also observed in the crosses compared with the controls when grown under salt and water‐limitation stresses. Discussion Overall, these results suggest the combinatorial effect of overexpressing MIOX4 and AVP1 may be more advantageous than the individual traits for enhancing stress tolerance and seed yields during crop improvement.

No abstract

Plant-produced volatile compounds play important roles in plant signaling and in the communication of plants with other organisms. Many plants emit green leaf volatiles (GLVs) in response to damage or attack, which serve to warn neighboring plants or attract predatory or parasitic insects to help defend against insect pests. GLVs include aldehydes, esters, and alcohols of 6-carbon compounds that are released rapidly following wounding. One GLV produced by maize (Zea mays) is the volatile (Z)-3-hexenal; this volatile is produced from the cleavage of (9Z,11E,15Z)-octadecatrienoic acid by hydroperoxide lyases (HPLs) of the cytochrome P450 CYP74B family. The specific HPL in maize involved in (Z)-3-hexenal production had not been determined. In this study, we used phylogenetics with known HPLs from other species to identify a candidate HPL from maize (ZmHPL). To test the ability of the putative HPL to produce (Z)-3-hexenal, we constitutively expressed the gene in Arabidopsis thaliana ecotype Columbia-0 that contains a natural loss-of-function mutant in AtHPL and examined the transgenic plants for restored (Z)-3-hexenal production. Volatile analysis of leaves from these transgenic plants showed that they did produce (Z)-3-hexenal, confirming that ZmHPL can produce (Z)-3-hexenal in vivo. Furthermore, we used gene expression analysis to show that expression of ZmHPL is induced in maize in response to both wounding and the insect pests Spodoptera frugiperda and Spodoptera exigua. Our study demonstrates that ZmHPL can produce GLVs and highlights its likely role in (Z)-3-hexenal production in response to mechanical damage and herbivory in maize.