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Lettuce cultivation requires high fertilizer inputs, which impact the environment and costs. Arbuscular mycorrhizal symbiosis (AMS) can reduce fertilizer use, enhance plant nutrition (especially phosphorus), and promote healthier plants. Class III peroxidases (PRXs) play crucial roles in various physiological processes and stress responses. However, their role in AMS and phosphorous (P) deficiency is still unclear. Our study identified 91 PRX genes in the lettuce genome (LsPRXs) and clustered them into eight subfamilies based on phylogenetic relationships. Evolutionary analysis indicated that tandem duplication was the main driver for LsPRX gene family expansion. Synteny analysis showed orthologous relationships of the PRX gene family between lettuce and potato, Arabidopsis, and maize, identifying 39, 28, and 3 shared PRXs, respectively. Transcriptomic data revealed that most LsPRX genes were more expressed in roots than in leaves and differentially expressed LsPRXs were found in response to AMS and P supply. Notably, 15% of LsPRX genes were differentially expressed in roots during mycorrhization. Gene expression network analysis highly correlated five LsPRXs (LsPRX17, LsPRX23, LsPRX24, LsPRX64, and LsPRX79) with genes involved in cell wall remodeling and reorganization during mycorrhization. Our results provide insights into the evolutionary history and functional roles of PRX genes in lettuce and identify candidate gene targets that may enhance the bio-stimulant effects of AMS and help to cope with P deficiency. [ABSTRACT FROM AUTHOR]

Stevia rebaudiana (Bertoni) is a highly valuable crop for the steviol glycoside content in its leaves, which are no-calorie sweeteners hundreds of times more potent than sucrose. The presence of health-promoting phenolic compounds, particularly flavonoids, in the leaf of S. rebaudiana adds further nutritional value to this crop. Although all these secondary metabolites are highly desirable in S. rebaudiana leaves, the genes regulating the biosynthesis of phenolic compounds and the shared gene network between the regulation of biosynthesis of steviol glycosides and phenolic compounds still need to be investigated in this species. To identify putative candidate genes involved in the synergistic regulation of steviol glycosides and phenolic compounds, four genotypes with different contents of these compounds were selected for a pairwise comparison RNA-seq analysis, yielding 1136 differentially expressed genes. Genes that highly correlate with both steviol glycosides and phenolic compound accumulation in the four genotypes of S. rebaudiana were identified using the weighted gene co-expression network analysis. The presence of UDP-glycosyltransferases 76G1, 76H1, 85C1, and 91A1, and several genes associated with the phenylpropanoid pathway, including peroxidase, caffeoyl-CoA O-methyltransferase, and malonyl-coenzyme A:anthocyanin 3-O-glucoside-6″-O-malonyltransferase, along with 21 transcription factors like SCL3, WRK11, and MYB111, implied an extensive and synergistic regulatory network involved in enhancing the production of such compounds in S. rebaudiana leaves. In conclusion, this work identified a variety of putative candidate genes involved in the biosynthesis and regulation of particular steviol glycosides and phenolic compounds that will be useful in gene editing strategies for increasing and steering the production of such compounds in S. rebaudiana as well as in other species. [ABSTRACT FROM AUTHOR]

The fig tree is a species particularly rich in volatile organic compounds, the production of which is becoming increasingly important for pharmaceutical purposes. This work was aimed at isolating genes related to the biosynthesis of furanocoumarins (especially psoralen) and terpenoids in the leaves of fig. Using gene sequences identified in other species, we performed an analysis of sequence similarity in the fig transcriptome and retrieved 49 genes, 13 related to the biosynthesis of furanocoumarins and 36 to that of terpenoids. The expression of these genes was studied by RNA-seq analysis in leaves of control and salt-treated plants. Most genes resulted regulated after salt treatment. Psoralen and terpenoids in the leaves were quantified by solid phase microextraction, and their concentration resulted correlated to the expression of genes putatively involved in their biosynthesis. These results will be useful for future breeding strategies to increase the production of fig volatile organic compounds. [ABSTRACT FROM AUTHOR]

Blackberries (Rubus spp.) are the fourth most economically important berry crop worldwide. Genome assemblies and annotations have been developed for Rubus species in subgenus Idaeobatus, including black raspberry (R. occidentalis), red raspberry (R. idaeus), and R. chingii, but very few genomic resources exist for blackberries and their relatives in subgenus Rubus. Here we present a chromosomelength assembly and annotation of the diploid blackberry germplasm accession "Hillquist" (R. argutus). "Hillquist" is the only known source of primocane-fruiting (annual-fruiting) in tetraploid fresh-market blackberry breeding programs and is represented in the pedigree of many important cultivars worldwide. The "Hillquist" assembly, generated using Pacific Biosciences long reads scaffolded with high-throughput chromosome conformation capture sequencing, consisted of 298Mb, of which 270Mb (90%) was placed on 7 chromosome-length scaffolds with an average length of 38.6Mb. Approximately 52.8% of the genome was composed of repetitive elements. The genome sequence was highly collinear with a novel maternal haplotype-resolved linkage map of the tetraploid blackberry selection A-2551TN and genome assemblies of R. chingii and red raspberry. A total of 38,503 protein-coding genes were predicted, of which 72% were functionally annotated. Eighteen flowering gene homologs within a previously mapped locus aligning to an 11.2Mb region on chromosome Ra02 were identified as potential candidate genes for primocane-fruiting. The utility of the "Hillquist" genome has been demonstrated here by the development of the first genotyping-by-sequencing-based linkage map of tetraploid blackberry and the identification of possible candidate genes for primocane-fruiting. This chromosome-length assembly will facilitate future studies in Rubus biology, genetics, and genomics and strengthen applied breeding programs. [ABSTRACT FROM AUTHOR]