Induction, identification and genetics analysis of tetraploid Actinidia chinensis

Polyploid Induction and Identification of Rosa roxburghii f. eseiosa

Rosa roxburghii f. eseiosa Ku is a variety of Rosa roxburghii, with two known genotypes: Wuci 1 and Wuci 2. The lack of prickle on the peel of R. roxburghii f. eseiosa makes it easy to pick and process, but its fruit size is small. Therefore, we aim to induce polyploidy in order to obtain a larger fruit variety of R. roxburghii f. eseiosa. In this study, current-year stems of Wuci 1 and Wuci 2 were used as materials for polyploid induction, which was carried out through colchicine treatment coupled with tissue culture and rapid propagation technology. Impregnation and smearing methods were effectively used to produce polyploids. Using flow cytometry and a chromosome counting method, it was found that one autotetraploid of Wuci 1 (2n = 4x = 28) was obtained by the impregnation method before primary culture, with a variation rate of 1.11%. Meanwhile, seven Wuci 2 bud mutation tetraploids (2n = 4x = 28) were produced by smearing methods during the training seedling stage. When tissue-culture seedlings were treated with 20 mg/L colchicine for 15 days, the highest polyploidy rate was up to 60%. Morphological differences between different ploidys were observed. The side leaflet shape index, guard cell length, and stomatal length of the Wuci 1 tetraploid were significantly different from those of the Wuci 1 diploid. The terminal leaflet width, terminal leaflet shape index, side leaflet length, side leaflet width, guard cell length, guard cell width, stomatal length, and stomatal width of the Wuci 2 tetraploid were significantly different from those of the Wuci 2 diploid. Additionally, the leaf color of the Wuci 1 and Wuci 2 tetraploids changed from light to dark, with an initial decrease in chlorophyll content followed by an increase. In summary, this study established an effective method for inducing polyploids in R. roxburghii f. eseiosa, which could provide a foundation for the breeding and development of new genetic resources for R. roxburghii f. eseiosa and other R. roxburghii varieties in the future.

Transcriptome Analysis of the Salt-Treated Actinidia deliciosa (A. Chev.) C. F. Liang and A. R. Ferguson Plantlets

The area of saline land in the world is quite large, and there is broad room for its development and usage. 'Xuxiang' is an Actinidia deliciosa variety that is tolerant to salt and can be planted in an area of light-saline land, and has good comprehensive characteristics and high economic value. However, the molecular mechanism of salt tolerance is unknown at present. To understand the molecular mechanism of salt tolerance, the leaves of A. deliciosa 'Xuxiang' were used as explants to establish a sterile tissue culture system, and plantlets were obtained using this system. One percent concentration (w/v) of sodium chloride (NaCl) was employed to treat the young plantlets cultured in Murashige and Skoog (MS) medium, then RNA-seq was used for transcriptome analysis. The results showed that the genes related to salt stress in the phenylpropanoid biosynthesis pathway and the anabolism of trehalose and maltose pathways were up-regulated; however, those genes in the plant hormone signal transduction and metabolic pathways of starch, sucrose, glucose, and fructose were down-regulated after salt treatment. The expression levels of ten genes that were up-regulated and down-regulated in these pathways were confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The salt tolerance of A. deliciosa might be related to the expression level changes in the genes in the pathways of plant hormone signal transduction, phenylpropanoid biosynthesis, and starch, sucrose, glucose, and fructose metabolism. The increased expression levels of the genes encoding alpha-trehalose-phosphate synthase, trehalose-phosphatase, alpha-amylase, beta-amylase, feruloyl-CoA 6-hydroxylase, ferulate 5-hydroxylase, and coniferyl-alcohol glucosyl transferase might be vital to the salt stress response of the young A. deliciosa plants.

Transcriptome Analysis of Low-Temperature-Treated Tetraploid Yellow Actinidia chinensis Planch. Tissue Culture Plantlets

Simple Summary

Yellow kiwifruit (Actinidia chinensis Planch.) is popular in the market. However, it is highly susceptible to severe weather, including as low temperatures and frost, which may affect its production in the coming year. The cold-resistant mechanism of yellow kiwifruit associated with gene regulation is poorly investigated. To better understand cold-adaptive mechanisms, we grew plants under low-temperature conditions, which was followed by transcriptome analysis to discern the genes that play an active role in growth under low temperatures. The findings and dataset obtained in this study advance our knowledge of the cold-adaptive genes in regulatory networks and helps us to understand the cold-tolerance mechanisms in the tetraploid yellow kiwifruit.

Abstract

The cold-resistant mechanism of yellow kiwifruit associated with gene regulation is poorly investigated. In this study, to provide insight into the causes of differences in low-temperature tolerance and to better understand cold-adaptive mechanisms, we treated yellow tetraploid kiwifruit ‘SWFU03’ tissue culture plantlets at low temperatures, used these plantlets for transcriptome analysis, and validated the expression levels of ten selected genes by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. A number of 1630 differentially expressed genes (DEGs) were identified, of which 619 pathway genes were up-regulated, and 1011 were down-regulated in the cold treatment group. The DEGs enriched in the cold tolerance-related pathways mainly included the plant hormone signal transduction and the starch and sucrose metabolism pathway. RT-qPCR analysis confirmed the expression levels of eight up-regulated genes in these pathways in the cold-resistant mutants. In this study, cold tolerance-related pathways (the plant hormone signal transduction and starch and sucrose metabolism pathway) and genes, e.g., CEY00_Acc03316 (abscisic acid receptor PYL), CEY00_Acc13130 (bZIP transcription factor), CEY00_Acc33627 (TIFY protein), CEY00_Acc26744 (alpha-trehalose-phosphate synthase), CEY00_Acc28966 (beta-amylase), CEY00_Acc16756 (trehalose phosphatase), and CEY00_Acc08918 (beta-amylase 4) were found.

Characterizing Tetraploid Populations of Actinidia chinensis for Kiwifruit Genetic Improvement

Understanding genetic diversity and structure in natural populations and their suitable habitat response to environmental changes is critical for the protection and utilization of germplasm resources. We evaluated the genetic diversity and structure of 24 A. chinensis populations using simple sequence repeat (SSR) molecular markers. The potential suitable distribution of tetraploid A. chinensis estimated under the current climate and predicted for the future climate was generated with ecological niche modeling (ENM). The results indicated that the polyploid populations of A.chinensis have high levels of genetic diversity and that there are distinct eastern and western genetic clusters. The population structure of A. chinensis can be explained by an isolation-by-distance model. The results also revealed that potentially suitable areas of tetraploids will likely be gradually lost and the habitat will likely be increasingly fragmented in the future. This study provides an extensive overview of tetraploid A. chinensis across its distribution range, contributing to a better understanding of its germplasm resources. These results can also provide the scientific basis for the protection and sustainable utilization of kiwifruit wild resources.

Transcriptome analysis of diploid and triploid Populus tomentosa

Triploid Chinese white poplar (Populus tomentosa Carr., Salicaceae) has stronger advantages in growth and better stress resistance and wood quality than diploid P. tomentosa. Using transcriptome sequencing technology to identify candidate transcriptome-based markers for growth vigor in young tree tissue is of great significance for the breeding of P. tomentosa varieties in the future. In this study, the cuttings of diploid and triploid P. tomentosa were used as plant materials, transcriptome sequencing was carried out, and their tissue culture materials were used for RT-qPCR verification of the expression of genes. The results showed that 12,240 differentially expressed genes in diploid and triploid P. tomentosa transcripts were annotated and enriched into 135 metabolic pathways. The top six pathways that enriched the most significantly different genes were plant-pathogen interaction, phenylpropanoid biosynthesis, MAPK signalling pathway-plant, ascorbate and aldarate metabolism, diterpenoid biosynthesis, and the betalain biosynthesis pathway. Ten growth-related genes were selected from pathways of plant hormone signal transduction and carbon fixation in photosynthetic organisms for RT-qPCR verification. The expression levels of MDH and CYCD3 in tissue-cultured and greenhouse planted triploid P. tomentosa were higher than those in tissue-cultured diploid P. tomentosa, which was consist ent with the TMM values calculated by transcriptome.

Enhancing the expression of ARK1 genes in poplar leads to multiple branches and transcriptomic changes

The ARBORKNOX1 (ARK1) gene is an important gene for regulating plant growth and development; however, transcriptomic responses of enhancing expression of ARK1 gene in poplar are poorly investigated. To provide insight into the gene function of the ARK1 gene in poplar, the ARK1 transgenic poplar '717' and '84 K' lines were obtained, the morphology of transgenic plants was observed, and transcriptome profiles were compared. The results showed that there were multiple branches in ARK1 transgenic seedlings compared with non-transgenic seedlings. The results of transcriptome analysis showed that there were significant differences in transcriptome profiles between the transgenic lines of '717' and '84 K', and between non-transgenic lines (CK) and transgenic plants. The real-time quantitative polymerase chain reaction (RT-qPCR) analysis confirmed the expression levels of the genes involved in the pathway of zeatin biosynthesis and brassinosteroid biosynthesis. The increase in expression levels of AHP and CYCD3 was related to multiple branches. Enhancing the expression of the ARK1 gene in poplar seedlings leads to multiple branches and transcriptomic changes.