Development, progress and future prospects in cryobiotechnology of Lilium spp

Exploring Agrobacterium-mediated genetic transformation methods and its applications in Lilium

As a typical bulb flower, lily is widely cultivated worldwide because of its high ornamental, medicinal and edible value. Although breeding efforts evolved over the last 10000 years, there are still many problems in the face of increasing consumer demand. The approach of biotechnological methods would help to solve this problem and incorporate traits impossible by conventional breeding. Target traits are dormancy, development, color, floral fragrance and resistances against various biotic and abiotic stresses, so as to improve the quality of bulbs and cut flowers in planting, cultivation, postharvest, plant protection and marketing. Genetic transformation technology is an important method for varietal improvement and has become the foundation and core of plant functional genomics research, greatly assisting various plant improvement programs. However, achieving stable and efficient genetic transformation of lily has been difficult worldwide. Many gene function verification studies depend on the use of model plants, which greatly limits the pace of directed breeding and germplasm improvement in lily. Although significant progress has been made in the development and optimization of genetic transformation systems, shortcomings remain. Agrobacterium-mediated genetic transformation has been widely used in lily. However, severe genotypic dependence is the main bottleneck limiting the genetic transformation of lily. This review will summarizes the research progress in the genetic transformation of lily over the past 30 years to generate the material including a section how genome engineering using stable genetic transformation system, and give an overview about recent and future applications of lily transformation. The information provided in this paper includes ideas for optimizing and improving the efficiency of existing genetic transformation methods and for innovation, provides technical support for mining and identifying regulatory genes for key traits, and lays a foundation for genetic improvement and innovative germplasm development in lily.

Extraction, purification, structural characteristics, biological activities, and applications of polysaccharides from the genus Lilium: A review

The genus Lilium (Lilium) has been widely used in East Asia for over 2000 years due to its rich nutritional and medicinal value, serving as both food and medicinal ingredient. Polysaccharides, as one of the most important bioactive components in Lilium, offer various health benefits. Recently, polysaccharides from Lilium plants have garnered significant attention from researchers due to their diverse biological properties including immunomodulatory, anti-oxidant, anti-diabetic, anti-tumor, anti-bacterial, anti-aging and anti-radiation effects. However, the limited comprehensive understanding of polysaccharides from Lilium plants has hindered their development and utilization. This review focuses on the extraction, purification, structural characteristics, biological activities, structure-activity relationships, applications, and relevant bibliometrics of polysaccharides from Lilium plants. Additionally, it delves into the potential development and future research directions. The aim of this article is to provide a comprehensive understanding of polysaccharides from Lilium plants and to serve as a basis for further research and development as therapeutic agents and multifunctional biomaterials.

Regulatory mechanism of the miR172e-LbrAP2 module during the vegetative growth phase transition in Lilium

MAIN CONCLUSION

It was proved for the first time that the miR172e-LbrAP2 module regulated the vegetative growth phase transition in Lilium, which provided a new approach to shorten the juvenile stage of Lilium, improved the reproduction rate, and reduced the propagation cost of Lilium commercial bulbs. Lilium is an ornamental bulb plant that takes at least 3 years to cultivate into commercial seed bulbs under natural conditions. The aim of this study was to shorten the Lilium expansion cycle. In this study, the growth cycle of lily tubers induced by low temperature of 15 °C was significantly shorter than that of tubers grown at a conventional temperature. Quantitative real-time PCR analysis showed that the expression patterns of miR172e and LbrAP2 were negatively correlated. GUS histochemical staining confirmed that miR172e and LbrAP2 in tobacco leaves interacted with each other after co-transformation. The shear sites of miR172e and its target gene, LbrAP2, upon binding, were identified by RLM 5' RACE analysis. In addition, miR172e and LbrAP2 showed opposite expression patterns after the transformation of Arabidopsis. miR172e overexpression accelerated the transition from juvenile to adult plants, whereas LbrAP2 overexpression inhibited this process, thus indicating that miR172e negatively regulated the target gene LbrAP2. Upregulation of the transcription factor LbrAP2 delayed the phase transition of plants, whereas miR172 inhibited the transcriptional translation of LbrAP2, thereby accelerating the phase transition. Low-temperature treatment of Lilium bulbs can shorten Lilium development, which provides a new approach to accelerating Lilium commercial bulb breeding and reducing breeding costs.

The Cryopreservation of Medicinal and Ornamental Geophytes: Application and Challenges

Nowadays, plant genetic resources are often at risk of loss and destruction. Geophytes are herbaceous or perennial species that are annually renewed by bulbs, rhizomes, tuberous roots, or tubers. They are often subject to overexploitation, which, combined with other biotic and abiotic stresses, can make these plants more vulnerable to a decline in their diffusion. As a result, multiple endeavors have been undertaken to establish better conservation strategies. Plant cryopreservation at ultra-low temperatures in liquid nitrogen (-196 °C) has proven to be an effective, long-term, low-cost, and suitable conservation method for many plant species. Over the last two decades, major advances in cryobiology studies have enabled successful explants of multiple genera and types, including pollen, shoot tips, dormant buds, and zygotic and somatic embryos. This review provides an update on recent advances and developments in cryopreservation and its application to medicinal and ornamental geophytes. In addition, the review includes a brief summary of factors limiting the success of bulbous germplasm conservation. The critical analysis underpinning this review will benefit biologists and cryobiologists in their further studies on the optimization of geophyte cryopreservation protocols and will support a more complete and wider application of knowledge in this area.

Full-Length Transcriptome Characterization and Functional Analysis of Pathogenesis-Related Proteins in Lilium Oriental Hybrid 'Sorbonne' Infected with Botrytis elliptica

Gray mold (Botrytis elliptica) causes a deleterious fungal disease that decreases the ornamental value and yield of lilies. Lilium oriental hybrid 'Sorbonne' is a variety that is resistant to gray mold. Understanding the mechanism of resistance against B. elliptica infection in 'Sorbonne' can provide a basis for the genetic improvement in lily plants. In this study, a PacBio Sequel II system was used to sequence the full-length transcriptome of Lilium 'Sorbonne' after inoculation with B. elliptica. A total of 46.64 Gb subreads and 19,102 isoforms with an average length of 1598 bp were obtained. A prediction analysis revealed 263 lncRNAs, and 805 transcription factors, 4478 simple sequence repeats, and 17,752 coding sequences were identified. Pathogenesis-related proteins (PR), which may play important roles in resistance against B. elliptica infection, were identified based on the full-length transcriptome data and previously obtained second-generation transcriptome data. Nine non-redundant potential LhSorPR proteins were identified and assigned to two groups that were composed of two LhSorPR4 and seven LhSorPR10 proteins based on their genetic relatedness. The real-time quantitative reverse transcription PCR (qRT-PCR) results showed that the patterns of expression of nine differentially expressed PR genes under B. elliptica stress were basically consistent with the results of transcriptome sequencing. The pattern of expression of LhSorPR4s and LhSorPR10s genes in different tissues was analyzed, and the expression of each gene varied. Furthermore, we verified the function of LhSorPR4-2 gene in Lilium. The expression of LhSorPR4-2 was induced by phytohormones such as methyl jasmonate, salicylic acid, and ethephon. Moreover, the promoter region of LhSorPR4-2 was characterized by several functional domains associated with phytohormones and stress response. The overexpression of LhSorPR4-2 gene in 'Sorbonne' increased the resistance of the lily plant to B. elliptica and correlated with high chitinase activity. This study provides a full-length transcript database and functionally analyzed the resistance of PR gene to B. elliptica in Lilium, thereby introducing the candidate gene LhSorPR4-2 to breed resistance in Lilium.

Cryopreservation of Endangered Ornamental Plants and Fruit Crops from Tropical and Subtropical Regions

Simple Summary

The protection of biodiversity, i.e., the biological variety and variability of life on Earth, is of great importance for the present and future generations. Maintaining variation at the genetic and ecosystem levels is indispensable in breeding programs and creation of new cultivars. Currently, numerous plant species, wild varieties, and local forms of ornamental and fruit plants are endangered with extinction. Cryopreservation, i.e., the storage of biological samples in tanks filled with liquid nitrogen is considered as the most effective long-term preservation method of plant genetic resources. Nonetheless, the establishment of efficient cryogenic procedures is a difficult task, requiring consideration of several factors. The impact of cryopreservation on the stability and homogeneity of the stored samples is of particular interest. The aim of this article is to evaluate some traditional and modern cryopreservation methods and their utility for the storage and exchange of genetic sources of tropical and subtropical horticultural crops.

Abstract

Horticultural crops comprise various economic species extending from fruits, nuts, vegetables, spices and condiments, ornamentals, aromatic, and medicinal plants. Ornamental and fruit plants are produced mainly for their nutritional and aesthetic values, respectively. Unfortunately, many tropical and subtropical species are in danger of extinction because of climate change and (a)biotic stresses. It is imperative to preserve the germplasms of these species for the present and future genetic improvement programs. Cryopreservation, i.e., maintenance of tissues at the ultralow temperature of liquid nitrogen, is a promising long-term preservation technique, alternative to seed or in vitro banks, which can be applied for both vegetatively and generatively (through seeds) propagated crops, including those with recalcitrant seeds. It is a technology of choice not only for the preservation of plant biodiversity but also for virus elimination in the proficient administration of large-scale micropropagation. The main advantages of cryopreservation are the lowering of in vitro culture expenditures, needed space, contamination risk, and operator errors. However, tropical species are temperature delicate and one of the foremost challenging issues is preconditioning treatments that stimulate physiological reactions to sufficiently enhance tolerance to dehydration and cryogenic procedures. In recent years, several cryopreservation methods based on encapsulation-vitrification, droplet-vitrification, the use of aluminum cryo-plates, and cryo-mesh have been established. Combined cryo-techniques, gene/DNA conservation, as well as studies on perceiving bio-molecular events and exploring the multistage process from the beginning to end of cryopreservation are receiving more emphasis. The development of cryobiomics delivers a conceptual framework to assess the significance of cell signaling mechanisms on cellular functions, the influence of cryoinjury factors on sample viability, and the implications for genetic stability following cryo-storage. The aim of this mini-review article is to provide a succinct synthesis of the developed cryogenic procedures and their use for the storage and exchange of genetic resources of tropical and subtropical horticultural crops, particularly fruit crops and ornamental plants under the threat of extinction.

Earthworm activity optimized the rhizosphere bacterial community structure and further alleviated the yield loss in continuous cropping lily (Lilium lancifolium Thunb.)

The soil microbial community plays a vital role in the biogeochemical cycles of bioelements and maintaining healthy soil conditions in agricultural ecosystems. However, how the soil microbial community responds to mitigation measures for continuous cropping obstacles remains largely unknown. Here we examined the impact of quicklime (QL), chemical fungicide (CF), inoculation with earthworm (IE), and a biocontrol agent (BA) on the soil microbial community structure, and the effects toward alleviating crop yield decline in lily. High-throughput sequencing of the 16S rRNA gene from the lily rhizosphere after 3 years of continuous cropping was performed using the Illumina MiSeq platform. The results showed that Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chloroflexi and Gemmatimonadetes were the dominant bacterial phyla, with a total relative abundance of 86.15-91.59%. On the other hand, Betaproteobacteriales, Rhizobiales, Myxococcales, Gemmatimonadales, Xanthomonadales, and Micropepsales were the dominant orders with a relative abundance of 28.23-37.89%. The hydrogen ion concentration (pH) and available phosphorus (AP) were the key factors affecting the structure and diversity of the bacterial community. The yield of continuous cropping lily with using similar treatments decreased yearly for the leaf blight, but that of IE was significantly (p < 0.05) higher than with the other treatments in the same year, which were 17.9%, 18.54%, and 15.69% higher than that of blank control (CK) over 3 years. In addition, IE significantly (p < 0.05) increased organic matter (OM), available nitrogen (AN), AP, and available potassium (AK) content in the lily rhizosphere soil, optimized the structure and diversity of the rhizosphere bacterial community, and increased the abundance of several beneficial bacterial taxa, including Rhizobiales, Myxococcales, Streptomycetales and Pseudomonadales. Therefore, enriching the number of earthworms in fields could effectively optimize the bacterial community structure of the lily rhizosphere soil, promote the circulation and release in soil nutrients and consequently alleviate the loss of continuous cropping lily yield.

Epigenetic and Genetic Integrity, Metabolic Stability, and Field Performance of Cryopreserved Plants

Cryopreservation is considered an ideal strategy for the long-term preservation of plant genetic resources. Significant progress was achieved over the past several decades, resulting in the successful cryopreservation of the genetic resources of diverse plant species. Cryopreservation procedures often employ in vitro culture techniques and require the precise control of several steps, such as the excision of explants, preculture, osmo- and cryoprotection, dehydration, freeze-thaw cycle, unloading, and post-culture for the recovery of plants. These processes create a stressful environment and cause reactive oxygen species (ROS)-induced oxidative stress, which is detrimental to the growth and regeneration of tissues and plants from cryopreserved tissues. ROS-induced oxidative stresses were documented to induce (epi)genetic and somatic variations. Therefore, the development of true-to-type regenerants of the source germplasm is of primary concern in the application of plant cryopreservation technology. The present article provides a comprehensive assessment of epigenetic and genetic integrity, metabolic stability, and field performance of cryopreserved plants developed in the past decade. Potential areas and the directions of future research in plant cryopreservation are also proposed.

Deciphering the Epigenetic Alphabet Involved in Transgenerational Stress Memory in Crops

Although epigenetic modifications have been intensely investigated over the last decade due to their role in crop adaptation to rapid climate change, it is unclear which epigenetic changes are heritable and therefore transmitted to their progeny. The identification of epigenetic marks that are transmitted to the next generations is of primary importance for their use in breeding and for the development of new cultivars with a broad-spectrum of tolerance/resistance to abiotic and biotic stresses. In this review, we discuss general aspects of plant responses to environmental stresses and provide an overview of recent findings on the role of transgenerational epigenetic modifications in crops. In addition, we take the opportunity to describe the aims of EPI-CATCH, an international COST action consortium composed by researchers from 28 countries. The aim of this COST action launched in 2020 is: (1) to define standardized pipelines and methods used in the study of epigenetic mechanisms in plants, (2) update, share, and exchange findings in epigenetic responses to environmental stresses in plants, (3) develop new concepts and frontiers in plant epigenetics and epigenomics, (4) enhance dissemination, communication, and transfer of knowledge in plant epigenetics and epigenomics.

Cryopreservation of shoot tips, evaluations of vegetative growth, and assessments of genetic and epigenetic changes in cryo-derived plants of Actinidia spp

A droplet-vitrification protocol was described for cryopreservation of shoot tips of kiwifruit 'Yuxiang' (Actinidia chinensis var. deliciosa). No significant differences were found in root formation and shoot growth between the in vitro-derived shoots (the control) and cryo-derived ones when cultured in vitro. No significant differences were detected in survival and vegetative growth between the in vitro-derived plants (the control) and cryo-derived ones after re-establishment in greenhouse conditions. Inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) did not detect any polymorphic bands in the cryo-derived shoots when cultured in vitro and the cryo-derived plants after re-establishment in greenhouse conditions. These data indicate rooting ability, vegetative growth and genetic stability are maintained in the cryo-derived kiwifruit plants recovered from the droplet-vitrification cryopreservation. Methylation sensitive amplification polymorphism (MSAP) detected 12.8% and 1.6% DNA methylation in the cryo-derived shoots when cultured in vitro and the cryo-derived plants after re-established in greenhouse conditions, respectively. This droplet-vitrification was applied to five cultivars and three rootstocks belonging to A. chinensis var. deliciosa, A. chinensis var. chinensis, A. macrosperma, A. polygama and A. valvata. The highest (68.3%) and lowest (22.5%) shoot regrowth were obtained in A. macrosperma and A. chinensis var. chinensis 'Jinmi', respectively, with an average of 46.4% shoot regrowth obtained across the eight genotypes. The droplet-vitrification protocol described here can be considered the most applicable cryopreservation method so far reported for the genus Actinidia. Results reported here provide theoretical and technical supports for setting up cryo-banks of genetic resources of Actinidia spp.