SDG26 Is Involved in Trichome Control in Arabidopsis thaliana: Affecting Phytohormones and Adjusting Accumulation of H3K27me3 on Genes Related to Trichome Growth and Development

DNA Methylation of the Autonomous Pathway Is Associated with Flowering Time Variations in Arabidopsis thaliana

Plant flowering time is affected by endogenous and exogenous factors, but its variation patterns among different populations of a species has not been fully established. In this study, 27 Arabidopsis thaliana accessions were used to investigate the relationship between autonomous pathway gene methylation, gene expression and flowering time variation. DNA methylation analysis, RT-qPCR and transgenic verification showed that variation in the flowering time among the Arabidopsis populations ranged from 19 to 55 days and was significantly correlated with methylation of the coding regions of six upstream genes in the autonomous pathway, FLOWERING LOCUS VE (FVE), FLOWERING LOCUS Y (FY), FLOWERING LOCUS D (FLD), PEPPER (PEP), HISTONE DEACETYLASE 5 (HAD5) and Pre-mRNA Processing Protein 39-1 (PRP39-1), as well as their relative expression levels. The expression of FVE and FVE(CS) was modified separately through degenerate codon substitution of cytosine and led to earlier flowering of transgenic plants by 8 days and 25 days, respectively. An accurate determination of methylated sites in FVE and FVE(CS) among those transgenic plants and the recipient Col-0 verified the close relationship between the number of methylation sites, expression and flowering time. Our findings suggest that the methylation variation of these six key upstream transcription factors was associated with the gene expression level of the autonomous pathway and flowering time in Arabidopsis. The FVE(CS) and FVE genes in transgenic plants tended to be hypermethylated, which could be a protective mechanism for plants. However, modification of gene sequences through degenerate codon substitution to reduce cytosine can avoid hypermethylated transferred genes in transgenic plants. It may be possible to partially regulate the flowering of plants by modified trans-epigenetic technology.

Identification of the Gossypium hirsutum SDG Gene Family and Functional Study of GhSDG59 in Response to Drought Stress

SET-domain group histone methyltransferases (SDGs) are known to play crucial roles in plant responses to abiotic stress. However, their specific function in cotton's response to drought stress has not been well understood. This study conducted a comprehensive analysis of the SDG gene family in Gossypium hirsutum, identifying a total of 82 SDG genes. An evolutionary analysis revealed that the SDG gene family can be divided into eight subgroups. The expression analysis shows that some GhSDG genes are preferentially expressed in specific tissues, indicating their involvement in cotton growth and development. The transcription level of some GhSDG genes is induced by PEG, with GhSDG59 showing significant upregulation upon polyethylene glycol (PEG) treatment. Quantitative polymerase chain reaction (qPCR) analysis showed that the accumulation of transcripts of the GhSDG59 gene was significantly upregulated under drought stress. Further functional studies using virus-induced gene silencing (VIGS) revealed that silencing GhSDG59 reduced cotton tolerance to drought stress. Under drought conditions, the proline content, superoxide dismutase (SOD) and peroxidase (POD) enzyme activities in the GhSDG59-silenced plants were significantly lower than in the control plants, while the malondialdehyde (MDA) content was significantly higher. Transcriptome sequencing showed that silencing the GhSDG59 gene led to significant changes in the expression levels of 1156 genes. The KEGG enrichment analysis revealed that these differentially expressed genes (DEGs) were mainly enriched in the carbon metabolism and the starch and sucrose metabolism pathways. The functional annotation analysis identified known drought-responsive genes, such as ERF, CIPK, and WRKY, among these DEGs. This indicates that GhSDG59 is involved in the drought-stress response in cotton by affecting the expression of genes related to the carbon metabolism and the starch and sucrose metabolism pathways, as well as known drought-responsive genes. This analysis provides valuable information for the functional genomic study of SDGs and highlights potential beneficial genes for genetic improvement and breeding in cotton.

Mapping and Detection of Genes Related to Trichome Development in Black Gram (Vigna mungo (L.) Hepper)

Black gram (Vigna mungo (L.) Hepper) is a pulses crop with good digestible protein and a high carbohydrate content, so it is widely consumed as human food and animal feed. Trichomes are large, specialized epidermal cells that confer advantages on plants under biotic and abiotic stresses. Genes regulating the development of trichomes are well characterized in Arabidopsis and tomato. However, little is known about trichome development in black gram. In this study, a high-density map with 5734 bin markers using an F2 population derived from a trichome-bearing and a glabrous cultivar of black gram was constructed, and a major quantitative trait locus (QTL) related to trichomes was identified. Six candidate genes were located in the mapped interval region. Fourteen single-nucleotide polymorphisms (SNPs) or insertion/deletions (indels) were associated with those genes. One indel was located in the coding region of the gene designated as Scaffold_9372_HRSCAF_11447.164. Real-time quantitative PCR (qPCR) analysis demonstrated that only one candidate gene, Scaffold_9372_HRSCAF_11447.166, was differentially expressed in the stem between the two parental lines. These two candidate genes encoded the RNA polymerase-associated protein Rtf1 and Bromodomain adjacent to zinc finger domain protein 1A (BAZ1A). These results provide insights into the regulation of trichome development in black gram. The candidate genes may be useful for creating transgenic plants with improved stress resistance and for developing molecular markers for trichome selection in black gram breeding programs.

QTL mapping and stability analysis of trichome density in zucchini (Cucurbita pepo L.)

Trichomes provide an excellent model for studying cell differentiation and proliferation. The aboveground tissues of plants with long dense trichomes (LDTs) can cause skin itching in people working in a zucchini field, in which management, pollination, and fruit harvesting are difficult. In this study, an F2 population was constructed with the LDT inbred line "16" and the sparse micro trichome (SMT) inbred line "63" for QTL analysis of type I and II trichome density. Two QTLs were identified on chromosomes 3 and 15 using the QTL-seq method. Additionally, 191 InDel markers were developed on 20 chromosomes, a genetic map was constructed for QTL mapping, and three QTLs were identified on chromosomes 3, 6, and 15. Two QTLs, CpTD3.1 and CpTD15.1, were identified in both QTL-seq and genetic map-based QTL analyses, and CpTD15.1 was the major-effect QTL. The stability of CpTD3.1 and CpTD15.1 was confirmed using data from F2 plants under different environmental conditions. The major-effect QTL CpTD15.1 was located between markers chr15-4991349 and chr15-5766791, with a physical distance of 775.44 kb, and explained 12.71%-29.37% of the phenotypic variation observed in the three environments. CpTD3.1 was located between markers chr3-218350 and chr3-2891236, in a region with a physical distance of 2,672.89 kb, and explained 5.00%-10.64% of the phenotypic variation observed in the three environments. The functional annotations of the genes within the CpTD15.1 region were predicted, and five genes encoding transcription factors regulating trichome development were selected. Cp4.1LG15g04400 encoded zinc finger protein (ZFP) and harbored nonsynonymous SNPs in the conserved ring finger domain between the two parental lines. There were significant differences in Cp4.1LG15g04400 expression between "16" and "63", and a similar pattern was found between germplasm resources of LDT lines and SMT lines. It was presumed that Cp4.1LG15g04400 might regulate trichome density in zucchini. These results lay a foundation for better understanding the density of multicellular nonglandular trichomes and the regulatory mechanism of trichome density in zucchini.

Development and Biomechanics of Grewia lasiocarpa E. Mey. Ex Harv. Trichomes Exudate

Grewia lasiocarpa E. Mey. Ex Harv., Malvaceae (forest raisin) is a tropical small tree or shrub valued for its ecological importance as well as its nutritional, antioxidant, antibacterial, and anti-cancer properties as well as its ecological and ornamental importance. Glandular and non-glandular trichomes are present on the fruits, stem bark and leaves of G. lasiocarpa and these trichomes are the first line of defense. They are important structures that plants use to combat biotic and abiotic stress. The development of G. lasiocarpa trichomes and the biomechanics of the exudates present in the glandular (capitate) trichome were investigated for the first time using advanced microscopy techniques [Scanning electron microscope (SEM) and Transmission electron microscope (TEM)]. The pressurized cuticular striations may play a role in the exudates' biomechanics, i.e., releasing secondary metabolites present in the capitate trichome, which was observed to be multidirectional. The presence of many glandular trichomes on a plant implies an increase in the amount of phytometabolites. A common precursor for the development of trichomes (non-glandular and glandular) was observed to be DNA synthesis associated with a periclinal cell division, thus the final fate of the cell is determined by cell cycle regulation, polarity, and expansion. The glandular trichomes of G. lasiocarpa are multicellular and polyglandular, while the non-glandular (glandless) trichomes are either single-celled or multicellular. Since, trichomes 'house' phytocompounds of medicinal, nutritional, and agronomical benefits; the molecular and genetic study of the glandular trichomes of Grewia lasiocarpa will be beneficial to humanity.