Fine Mapping and Functional Analysis of the Gene PcTYR, Involved in Control of Cap Color of Pleurotus cornucopiae

Identification and functional characterization of major gene pcmfs, controlling cap color formation in Pleurotus cornucopiae

Oyster mushrooms are grown commercially worldwide, especially in many developing countries, for their easy cultivation and high biological efficiency. Cap color is an important commercial trait for oyster mushrooms. Little is known about the genetic mechanism of the cap color trait in oyster mushrooms, which limits molecular breeding for the improvement of cap color-type cultivars. In this study, an important candidate gene, pcmfs, for cap color in the oyster mushroom Pleurotus cornucopiae was identified based on the results of QTL (quantitative trait loci) mapping and comparative transcriptome analysis of our previous research. The pcmfs gene belonged to major facilitator superfamily (MFS) and was localized to the cell membrane. Expression pattern analysis and overexpression experiment demonstrated that pcmfs played an important positive role in cap color formation, with high expression levels leading to dark cap color. To our knowledge, this is the first reported gene that may be involved in the melanin transport in edible fungi. The results will enhance our understanding of the genetic basis for cap color formation in oyster mushrooms, ultimately facilitating the targeted molecular breeding of this phenotypic trait.IMPORTANCEOyster mushrooms are widely cultivated worldwide, particularly in developing countries, owing to their straightforward cultivation requirements and high biological efficiency. Cap color represents a significant commercial trait of oyster mushrooms. Despite its significance, the genetic basis of this trait remains poorly understood, limiting progress in molecular breeding to diversify cap color variants. Bridging this knowledge gap could improve the market appeal and consumer satisfaction of these cultivars by facilitating targeted breeding strategies. In our previous research, a major QTL of cap color in oyster mushroom P. cornucopiae was mapped and DEGs (differentially expressed genes) between the dark strains and white strains were identified. Based on this, the candidate gene for cap color pcmfs was further mined. The pcmfs gene, belonging to the major facilitator superfamily (MFS), is localized to the cell membrane. Expression pattern analysis and overexpression experiments have shown that pcmfs plays a significant role in cap color formation. To our knowledge, this is the first reported gene that may be involved in the melanin transport in edible fungi. The results contribute to elucidate the genetic mechanisms governing cap color formation in mushrooms, advancing targeted molecular breeding for this trait.

Pan-genome analysis reveals genomic variations during enoki mushroom domestication, with emphasis on genetic signatures of cap color and stipe length

INTRODUCTION

The domestication of edible mushrooms, including Flammulina filiformis, offers valuable insights into the genetic changes driven by artificial selection. Understanding these changes is crucial for uncovering the mechanisms behind genome evolution in domesticated mushrooms.

OBJECTIVES

This study aims to investigate the population structure, genetic diversity, and domestication-related genomic changes in F. filiformis. By comparing the genome sequences of 199 wild and cultivated strains, we aim to elucidate the impact of domestication on F. filiformis.

METHODS

We performed de novo genome assembly and gene-based pan-genome analysis on the 199 strains, which included both wild and cultivated strains. We also conducted genome-wide association studies (GWAS) using presence-absence variation (PAV) and SNP data, combined with RNA sequencing, to identify genes associated with domestication traits, such as cap color and stipe length. Gene functional confirmation was achieved through genetic transformation experiments.

RESULTS

Our analysis grouped the strains into four distinct populations, which correlated with varying intensities of artificial selection. The three cultivated populations exhibited smaller genome sizes, fewer genes, lower genetic variation, reduced gene expression diversity, and lower heterozygosity compared to the wild population. The analysis revealed the loss of genes related to the beta-lactam antibiotic catabolic process and specific MAPK pathway genes during domestication, rendering domesticated strains more susceptible to diseases. Four genes closely associated with cap color and stipe length were identified, but genetic transformation experiments confirmed the functional relevance of only two (FfB and FfD) identified through PAV-based GWAS.

CONCLUSION

This study uncovered significant genomic variations between cultivated and wild F. filiformis populations, including the loss of pathogen resistance genes during domestication. We also identified key genes linked to cap color and stipe length, demonstrating for the first time the important role of PAV variation in mushroom domestication. These insights provide a foundation for future mushroom breeding and evolutionary research.

Quantitative trait loci analysis for molecular markers linked to agricultural traits of Pleurotus ostreatus

Pleurotus ostreatus is a global mushroom crop with nutritional and medicinal benefits. However, the genetic basis of several commercial traits remains unknown. To address this, we analyzed the quantitative trait loci (QTLs) for two representative cultivars, "Heuktari" and "Miso," with apparently distinct alleles. A genetic map with 11 linkage groups was constructed, in which 27 QTLs were assigned to 14 traits. The explained phenotypic variations in QTLs ranged from 7.8% to 22.0%. Relatively high LOD values of 6.190 and 5.485 were estimated for the pinheading period and the number of valid stipes, respectively. Some QTL-derived molecular markers showed potential enhancement rates of selection precision in inbred lines, especially for cap shape (50%) and cap thickness (30%). Candidate genes were inferred from the QTL regions and validated using qRT-PCR, particularly for the cysteine and glutathione pathway, in relation to cap yellowness. The molecular markers in this study are expected to facilitate the breeding of the Heuktari and Miso lines and provide probes to identify related genes in P. ostreatus.

Fine mapping of ClLOX, a QTL for powdery mildew resistance in watermelon (Citrullus lanatus L.)

KEY MESSAGE

ClLOX, is located on chromosome 2 and encodes a lipoxygenase gene, which induced watermelon powdery mildew resistance by inhibiting pathogen spread. Powdery mildew is one of the most severe fungal diseases reducing yield and quality of watermelon (Citrullus lanatus L.) and other cucurbit crops. Genes responsible for powdery mildew resistance in watermelon are highly valuable. In this study, we first identified the QTL pm-lox for powdery mildew resistance in watermelon, located within a 0.93 Mb interval of chromosome 2, via XP-GWAS method using two F2 populations. The F2:3 families from one of the F2 populations were then used for fine-mapping the pm-lox locus into a 9,883 bp physical region between 29,581,906 and 29,591,789, containing only two annotated genes. Of these, only ClG42_02g0161300 showed a significant differential expression between the resistant and susceptible lines after powdery mildew inoculation based on RNA sequencing (RNA-seq) and qRT-PCR analysis, and is designated ClLOX. Derived Cleaved Amplified Polymorphic Sequence (dCAPs) markers were developed and validated. In addition, our tests showed that the resistance was anti-spread rather than anti-infection of the pathogen. This study identified a new resistance gene (ClLOX), provided insights into the mechanism of powdery mildew resistance, and developed a molecular marker for watermelon breeding.

Silencing of Amylomyces rouxii aspartic II protease by siRNA to increase tyrosinase activity

Amylomyces rouxii is a zygomycete that produces extracellular protease and tyrosinase. The tyrosinase activity is negatively regulated by the proteases and, which attempts to purify the tyrosinase (tyr) enzyme that has been hampered by the presence of a protease that co-purified with it. In this work we identified genes encoding aspartic protease II (aspII) and VI of A. rouxii. Using an RNAi strategy based on the generation of a siRNA by transcription from two opposite-orientated promoters, the expression of these two proteases was silenced, showing that this molecular tool is suitable for gene silencing in Amylomyces. The transformant strains showed a significant attenuation of the transcripts (determined by RT-qPCR), with respective inhibition of the protease activity. In the case of aspII, inhibition was in the range of 43-90 % in different transformants, which correlated well with up to a five-fold increase in tyr activity with respect to the wild type and control strains. In contrast, silencing of aspVI caused a 43-65 % decrease in protease activity but had no significant effect on the tyr activity. The results show that aspII has a negative effect on tyr activity, and that the silencing of this protease is important to obtain strains with high levels of tyr activity.

Quantitative trait locus mapping and identification of candidate genes for resistance to Verticillium wilt in four recombinant inbred line populations of Gossypium hirsutum

Improving resistance to Verticillium wilt is of great significance for achieving high and stable yields of Upland cotton (Gossypium hirsutum). To deeply understand the genetic basis of cotton resistance to Verticillium wilt, Verticillium wilt-resistant Upland Lumianyan 28 and four Verticillium wilt-susceptible Acala cotton cultivars were used to create four recombinant inbred line (RIL) populations of 469 families through nested hybridization. Phenotypic data collected in five stressful environments were used to select resistant and sensitive lines and create a mixed pool of extreme phenotypes for BSA-seq. A total of 8 QTLs associated with Verticillium wilt resistance were identified on 4 chromosomes, of which qVW-A12-5 was detected simultaneously in the RIL populations and in one of the RIL populations and was identified for the first time. According to the sequence comparison and transcriptome analysis of candidate genes in the QTL interval between parents and pools, 4 genes were identified in the qVW-A12-5 interval. qRT-PCR of parental and phenotypically extreme lines revealed that Gh_CPR30 was induced by and may be a candidate gene for resistance to Verticillium wilt in G. hirsutum. Furthermore, VIGS technology revealed that the disease severity index (DSI) of the Gh_CPR30-silenced plants was significantly higher than that of the control. These results indicate that the Gh_CPR30 gene plays an important role in the resistance of G. hirsutum to Verticillium wilt, and the study provides a molecular basis for analyzing the molecular mechanism underlying G. hirsutum resistance to Verticillium wilt.