Water deprivation modifies the metabolic profile of lavender (Lavandula angustifolia Mill.) leaves.

Lavender plantation is globally expanded due to the increasing demand of its essential oil and its popularity as an ornamental species. However, lavender plantations, and consequently essential oil industries, are threatened by more frequent and severe drought episodes in a globally changing climate. Still little is known about the changes in the general metabolome, which provides the precursors of essential oil production, by extended drought events. Prolonged drought fundamentally results in yield losses and changing essential oil composition. In the present study, the general metabolome of a main cultivated lavender species (Lavandula angustifolia Mill.) in response to water deprivation (WD) and re-watering was analyzed to identify the metabolomics responses. We found prolonged WD resulted in significant accumulations of glucose, 1,6-anhydro-ß-D-glucose, sucrose, melezitose and raffinose, but declines of allulose, ß-D-allose, altrose, fructose and D-cellobiose accompanied by decreased organic acids abundances. Amino acids and aromatic compounds of p-coumaric acid, hydrocaffeic acid and caffeic acid significantly accumulated at prolonged WD, whereas aromatics of cis-ferulic acid, taxifolin and two fatty acids (i.e., palmitic acid and stearic acid) significantly decreased. Prolonged WD also resulted in decreased abundances of polyols, particularly myo-inositol, galactinol and arabitol. The altered metabolite profiles by prolonged WD were mostly not recovered after re-watering, except for branched-chain amino acids, proline, serine and threonine. Our study illustrates the complex changes of leaf primary and secondary metabolic processes of L. angustifolia by drought events and highlights the potential impact of these precursors of essential oil production on the lavender industry.

Teosinte confers specific alleles and yield potential to maize improvement.

KEY MESSAGE: Teosinte improves maize grain yield and broadens the maize germplasm. Seventy-one quantitative trait loci associated with 24 differential traits between maize and teosinte were identified. Maize is a major cereal crop with a narrow germplasm that has limited its production and breeding progress. Teosinte, an ancestor of maize, provides valuable genetic resources for maize breeding. To identify the favorable alien alleles in teosinte and its yield potential for maize breeding, 4 backcrossed maize-teosinte recombinant inbred line (RIL) populations were cultivated under five conditions. A North Carolina mating design II experiment was conducted on inbred lines with B73 and Mo17 pedigree backgrounds to analyze their combining ability. Abundant phenotypic variation on 26 traits of four RIL populations were found, of which barren tip length, kernel height, and test weight showed positive genetic improvement potential. The hybrid FM132 (BD138/MP116) showed a superior grain yield to that of the check, with an average yield gain of 4.86%. Moreover, inbred lines BD138 and MP048 showed a higher general grain yield combining ability than those of their corresponding checks. We screened 4,964,439 high-quality single-nucleotide polymorphisms in the BD (B73/Zea diploperennis) RIL population for bin construction and used 2322 bin markers for genetic map construction and quantitative trait loci (QTL) mapping. Via inclusive composite interval mapping, 71 QTL associated with 24 differential traits were identified. Gene annotation and transcriptional expression suggested that Zm00001eb352570 and Zm00001eb352580, both annotated as ethylene-responsive transcription factors, were key candidate genes that regulate ear height and the ratio of ear to plant height. Our results indicate that teosinte could broaden the narrow maize germplasm, improve yield potential, and provide desirable alleles for maize breeding.

Evolutionary conservation and functional divergence of the LFK gene family play important roles in the photoperiodic flowering pathway of land plants.

ZEITLUPE (ZTL), LOV KELCH PROTEIN 2 (LKP2), and FLAVIN-BINDING KELCH REPEAT F-BOX 1 (FKF1)-blue-light photoreceptors-play important roles in regulating the circadian clock and photoperiodic flowering pathway in plants. In this study, phylogenetic analysis revealed that the LOV (Light, Oxygen, or Voltage) and Kelch repeat-containing F-box (LFK) gene family can be classified into two clades, ZTL/LKP2 and FKF1, with clear differentiation between monocots and dicots within each clade. The LFK family genes underwent strong purifying selection; however, signatures of positive selection to adapt to local conditions still existed in 18 specific codons. In 87 diverse maize inbred lines, significant differences were identified (P ≤ 0.01) for days to female flowering between the haplotypes consisting of eight positive selection sites at ZmFKF1b corresponding to tropical and temperate maize groups of the phylogenetic tree, indicating a key role of ZmFKF1b in maize adaptive evolution. In addition, positive coevolution was detected in the domains of the LFK family for long-term cooperation to targets. The Type-I and Type-II functional divergence analysis revealed subfunctionalization or neofunctionalization of the LFKs, and the ZTL subfamily is most likely to maintain the ancestral function of LFKs. Over 50% of critical amino acid sites involved in the functional divergence were identified in the Kelch repeat domain, resulting in the distinction of substrates for ubiquitination and degradation. These results suggest that evolutionary conservation contributes to the maintenance of critical physiological functions, whereas functional divergence after duplication helps to generate diverse molecular regulation mechanisms.

Genome-wide characterization of non-reference transposable element insertion polymorphisms reveals genetic diversity in tropical and temperate maize.

BACKGROUND: Maize was originally domesticated in a tropical environment but is now widely cultivated at temperate latitudes. Temperate and tropical maize populations have diverged both genotypically and phenotypically. Tropical maize lines grown in temperate environments usually exhibit delayed flowering, pollination, and seed set, which reduces their grain yield relative to temperate adapted maize lines. One potential mechanism by which temperate maize may have adapted to a new environment is novel transposable element insertions, which can influence gene regulation. Recent advances in sequencing technology have made it possible to study variation in transposon content and insertion location in large sets of maize lines. RESULTS: In total, 274,408 non-redundant TEs (NRTEs) were identified using resequencing data generated from 83 maize inbred lines. The locations of DNA TEs and copia-superfamily retrotransposons showed significant positive correlations with gene density and genetic recombination rates, whereas gypsy-superfamily retrotransposons showed a negative correlation with these two parameters. Compared to tropical maize, temperate maize had fewer unique NRTEs but higher insertion frequency, lower background recombination rates, and higher linkage disequilibrium, with more NRTEs close to flowering and stress-related genes in the genome. Association mapping demonstrated that the presence/absence of 48 NRTEs was associated with flowering time and that expression of neighboring genes differed between haplotypes where a NRTE was present or absent. CONCLUSIONS: This study suggests that NRTEs may have played an important role in creating the variation in gene regulation that enabled the rapid adaptation of maize to diverse environments.

The complete chloroplast genome of Rubus pacificus (Rosaceae).

The complete chloroplast genome of Rubus pacificus, a representative species of R. sect. Malachobatus subsect. Stipulosi, has been characterized by reference-based assembly using Illumina paired-end data. The complete chloroplast genome is 156,255 bp in length, containing a large single-copy region (LSC) of 85,864 bp and a small single-copy region (SSC) of 18,849 bp, which are separated by a pair of inverted repeat regions (IR) of 25,771 bp. A total of 129 genes were predicted from the chloroplast genome, including 85 protein-coding genes, 36 tRNA genes, and eight rRNA genes. According to the present sampling, phylogenetic analysis reveals that R. pacificus and R. laciniatostipulatus form a strongly supported clade and R. sect. Malachobatus subsect. Stipulosi is not monophyletic.

Lateral mechanical impedance rather than frontal promotes cortical expansion of roots.

It has long been considered that mechanical impedance on root will restrict root elongation and consequently promote radial growth. When seedlings grew in sands, we did observe radial expansion of roots and it, however, arose before elongation restriction. Mechanical impedance of sands can be classified into frontal- and lateral-type based on the interaction site of root. Therefore, we suspected that radial expansion might be mainly stimulated by lateral- rather than frontal-impedance. To verify our speculation, roots were exposed to frontal- and lateral-impedance separately. Small plastic caps were used to provide pure frontal impedance on root tips and cylindrical plastic containers were used to provide pure lateral impedance. Root elongation was remarkably suppressed under the frontal impedance of plastic caps, and more than that in sand-condition. However, the radial expansion of the plastic-cap-fitted roots was far inferior to that of the sand-cultured roots. Microstructural analysis revealed that sand-condition thickened root largely dependents on cortical expansion, whereas plastic cap did it mainly by thickening stele. In cylindrical plastic containers, mechanical impedance came only from the lateral direction and promoted the expansion of cortex like sand-condition. Thus, we proposed that the expansion of cortex and the consequent radial growth of roots were mainly due to lateral impedance when seedlings grew in sands.

Nutritional and physicochemical characteristics of purple sweet corn juice before and after boiling.

Sweet corn juice is becoming increasingly popular in China. In order to provide valuable health-related information to consumers, the nutritional and physicochemical characteristics of raw and boiled purple sweet corn juices were herein investigated. Sugars, antinutrients, total free phenols, anthocyanins, and antioxidant activity were analyzed by conventional chemical methods. The viscosity and stability of juices were determined by Ubbelohde viscosity meter and centrifugation, respectively. Boiling process could elevate viscosity, stability and sugar content, and reduce antinutrients, total free phenols, anthocyanins, and antioxidant activity in corn juice. In addition, short time boiling efficiently reduced the degradation of anthocyanins during subsequent refrigeration. The content of amino acids, vitamin B1/B2 and E were detected by High Performance Liquid Chromatography. Gas Chromatography Mass Spectrometry was used for the analysis of fatty acids and aroma compounds. Several aroma compounds not previously reported in corn were identified, including 1-heptanol, 2-methyl-2-butenal, (Z)-3-nonen-1-ol, 3-ethyl-2-methyl-1,3-hexadiene, and 2,4-bis(1,1-dimethylethyl)phenol. Interestingly, the boiling process had no apparent effect on the amino acids profile, but it caused a 45.8% loss of fatty acids in the juice by promoting the retention of fatty acids in the corn residue. These results provide detailed information that could be used for increasing consumers' knowledge of sweet corn juice, further development of sweet corn juice by food producers, and maize breeding programs.

Genome-Wide Association Study of 13 Traits in Maize Seedlings under Low Phosphorus Stress.

CORE IDEAS: Low P stress is a global issue for grain production. Significant phenotypic differences were detected among 13 traits in 356 maize lines under P-sufficient and P-deficient conditions. Significant single nucleotide polymorphisms (SNPs) and low-P stress-responsive genes were identified for 13 maize root traits based on a genome-wide association study. Hap5, harboring 12 favorable SNPs, could enhance strong root systems and P absorption under low-P stress. Phosphorus is an essential macronutrient required for normal plant growth and development. Determining the genetic basis of root traits will enhance our understanding of maize's (Zea mays L.) tolerance to low-P stress. Here, we identified significant phenotypic differences for 13 traits in maize seedlings subjected to P-sufficient and P-deficient conditions. Six extremely sensitive and seven low-P stress tolerant inbreds were selected from 356 inbred lines of maize. No significant differences were observed between temperate and tropical-subtropical groups with respect to trait ratios associated with the adaptation to low-P stress. The broad-sense heritability of these traits ranged from relatively moderate (0.59) to high (0.90). Through genome-wide association mapping with 541,575 informative single nucleotide polymorphisms (SNPs), 551, 1140 and 1157 significant SNPs were detected for the 13 traits in 2012, 2016 and both years combined, respectively, along with 23 shared candidate genes, seven of which overlapped with reported quantitative trait loci and genes for low-P stress. Five haplotypes located in candidate gene GRMZM2G009544 were identified; among these, Hap5, harboring 12 favorable SNP alleles, showed significantly greater values for the root traits studied than the other four haplotypes under both experimental conditions. The candidate genes and favorable haplotypes and alleles identified here provide promising resources for genetic studies and molecular breeding for improving tolerance to abiotic stress in maize.