Thermal-stable proteins of fruit of long-living Sacred Lotus Nelumbo nucifera Gaertn var. China Antique

Lotus (Nelumbo nucifera): a multidisciplinary review of its cultural, ecological, and nutraceutical significance

This comprehensive review systematically examines the multifarious aspects of Nelumbo nucifera, elucidating its ecological, nutritional, medicinal, and biomimetic significance. Renowned both culturally and scientifically, Nelumbo nucifera manifests remarkable adaptability, characterized by its extensive distribution across varied climatic regions, underpinned by its robust rhizome system and prolific reproductive strategies. Ecologically, this species plays a crucial role in aquatic ecosystems, primarily through biofiltration, thereby enhancing habitat biodiversity. The rhizomes and seeds of Nelumbo nucifera are nutritionally significant, being rich sources of dietary fiber, essential vitamins, and minerals, and have found extensive culinary applications. From a medicinal perspective, diverse constituents of Nelumbo nucifera exhibit therapeutic potential, including anti-inflammatory, antioxidant, and anti-cancer properties. Recent advancements in preservation technology and culinary innovation have further underscored its role in the food industry, highlighting its nutritional versatility. In biomimetics, the unique "lotus effect" is leveraged for the development of self-cleaning materials. Additionally, the transformation of Nelumbo nucifera into biochar is being explored for its potential in sustainable environmental practices. This review emphasizes the critical need for targeted conservation strategies to protect Nelumbo nucifera against the threats posed by climate change and habitat loss, advocating for its sustainable utilization as a species of significant value.

Identification of YABBY Transcription Factors and Their Function in ABA and Salinity Response in Nelumbo nucifera

The plant-specific transcription factor family YABBY plays important roles in plant responses to biotic and abiotic stresses. Although the function of YABBY has been identified in many species, systematic analysis in lotus (Nelumbo nucifera) is still relatively lacking. The present study aimed to characterize all of the YABBY genes in lotus and obtain better insights into NnYABBYs in response to salt stress by depending on ABA signaling. Here, we identified nine YABBY genes by searching the whole lotus genome based on the conserved YABBY domain. Further analysis showed that these members were distributed on six different chromosomes and named from YABBY1 to YABBY9, which were divided into five subgroups, including YAB1, YAB2, YAB5, INO, and CRC. The analysis of cis-elements in promotors revealed that NnYABBYs could be involved in plant hormone signaling and plant responses to abiotic stresses. Quantitative real-time PCR (qRT-PCR) showed that NnYABBYs could be up-regulated or down-regulated by ABA, fluridone, and salt treatment. Subcellular localization indicated that NnYABBY4, NnYABBY5, and NnYABBY6 were mainly localized in the cell membrane and cytoplasm. In addition, the intrinsic trans-activity of NnYABBY was tested by a Y2H assay, which revealed that NnYABBY4, NnYABBY5, and NnYABBY6 are deprived of such a property. This study provided a theoretical basis and reference for the functional research of YABBY for the molecular breeding of lotus.

TMT-based quantitative proteomic and physiological analyses on lotus plumule of artificially aged seed in long-living sacred lotus Nelumbo nucifera

Seed longevity is important for the maintenance of seed nutritional quality, vigor, and germination potential during storage. Sacred lotus is known as one of the longest living seeds in the world and their ability to maintain longevity has been widely investigated. In this study, a suitable controlled deterioration treatment (CDT) method was first established to evaluate the vigor loss of lotus plumule (LP), and then the Tandem Mass Tags (TMT)-based proteomic analysis was performed on LP from the CDT-treated seed to quantitatively and qualitatively analyze the protein profile dynamic. In total, 4002 proteins were successfully quantified, of them, 558 differently accumulated proteins (DAPs) were identified. Protein processing and RNA-related proteins were found more easily to be affected by CDT, which may directly result in seed vigor loss. Meanwhile, CDT resulted in remarkable up-regulation of numerous proteins related to antioxidation, photosynthesis, RNA and DNA stability, starch and sucrose mobilization, and cell membrane and wall stability, which potentially played key roles in maintaining the lotus seed vigor under CDT. Histological and physiological analyses were also performed to verify some proteome results. This study provided both fundamental data and new insights to further uncover the secret of lotus seed longevity. SIGNIFICANCE: Seed aging affects the seed quality and can result in direct economic losses. The exceptional longevity of sacred lotus seed has attracted extensive attention. In this study, an optimized CDT method was used to mimic the natural aging process of sacred lotus seed, and based on TMT-based quantitative proteomic analysis on the LP profile of CDT-treated seeds, a series of differentially accumulation of specific proteins (DEPs) were revealed related to CDT resistance. Correspondingly, the physiological state and histological structure of the LP along with the CDT were detected to verify the proteome data. This study provided comprehensive information for the molecular basis of lotus seed aging analysis and facilitate to screen seed longevity related proteins for other plant species.

TMT-Based Quantitative Proteomic Analysis Reveals the Physiological Regulatory Networks of Embryo Dehydration Protection in Lotus (Nelumbo nucifera)

Lotus is an aquatic plant that is sensitive to water loss, but its seeds are longevous after seed embryo dehydration and maturation. The great difference between the responses of vegetative organs and seeds to dehydration is related to the special protective mechanism in embryos. In this study, tandem mass tags (TMT)-labeled proteomics and parallel reaction monitoring (PRM) technologies were used to obtain novel insights into the physiological regulatory networks during lotus seed dehydration process. Totally, 60,266 secondary spectra and 32,093 unique peptides were detected. A total of 5,477 proteins and 815 differentially expressed proteins (DEPs) were identified based on TMT data. Of these, 582 DEPs were continuously downregulated and 228 proteins were significantly up-regulated during the whole dehydration process. Bioinformatics and protein-protein interaction network analyses indicated that carbohydrate metabolism (including glycolysis/gluconeogenesis, galactose, starch and sucrose metabolism, pentose phosphate pathway, and cell wall organization), protein processing in ER, DNA repair, and antioxidative events had positive responses to lotus embryo dehydration. On the contrary, energy metabolism (metabolic pathway, photosynthesis, pyruvate metabolism, fatty acid biosynthesis) and secondary metabolism (terpenoid backbone, steroid, flavonoid biosynthesis) gradually become static status during lotus embryo water loss and maturation. Furthermore, non-enzymatic antioxidants and pentose phosphate pathway play major roles in antioxidant protection during dehydration process in lotus embryo. Abscisic acid (ABA) signaling and the accumulation of oligosaccharides, late embryogenesis abundant proteins, and heat shock proteins may be the key factors to ensure the continuous dehydration and storage tolerance of lotus seed embryo. Stress physiology detection showed that H2O2 was the main reactive oxygen species (ROS) component inducing oxidative stress damage, and glutathione and vitamin E acted as the major antioxidant to maintain the REDOX balance of lotus embryo during the dehydration process. These results provide new insights to reveal the physiological regulatory networks of the protective mechanism of embryo dehydration in lotus.

The complexity of alternative splicing and landscape of tissue-specific expression in lotus (Nelumbo nucifera) unveiled by Illumina- and single-molecule real-time-based RNA-sequencing

Alternative splicing (AS) plays a critical role in regulating different physiological and developmental processes in eukaryotes, by dramatically increasing the diversity of the transcriptome and the proteome. However, the saturation and complexity of AS remain unclear in lotus due to its limitation of rare obtainment of full-length multiple-splice isoforms. In this study, we apply a hybrid assembly strategy by combining single-molecule real-time sequencing and Illumina RNA-seq to get a comprehensive insight into the lotus transcriptomic landscape. We identified 211,802 high-quality full-length non-chimeric reads, with 192,690 non-redundant isoforms, and updated the lotus reference gene model. Moreover, our analysis identified a total of 104,288 AS events from 16,543 genes, with alternative 3ʹ splice-site being the predominant model, following by intron retention. By exploring tissue datasets, 370 tissue-specific AS events were identified among 12 tissues. Both the tissue-specific genes and isoforms might play important roles in tissue or organ development, and are suitable for ‘ABCE’ model partly in floral tissues. A large number of AS events and isoform variants identified in our study enhance the understanding of transcriptional diversity in lotus, and provide valuable resource for further functional genomic studies.

The Latest Studies on Lotus (Nelumbo nucifera)-an Emerging Horticultural Model Plant

Lotus (Nelumbo nucifera) is a perennial aquatic basal eudicot belonging to a small family Nelumbonaceace, which contains only one genus with two species. It is an important horticultural plant, with its uses ranging from ornamental, nutritional to medicinal values, and has been widely used, especially in Southeast Asia. Recently, the lotus obtained a lot of attention from the scientific community. An increasing number of research papers focusing on it have been published, which have shed light on the mysteries of this species. Here, we comprehensively reviewed the latest advancement of studies on the lotus, including phylogeny, genomics and the molecular mechanisms underlying its unique properties, its economic important traits, and so on. Meanwhile, current limitations in the research of the lotus were addressed, and the potential prospective were proposed as well. We believe that the lotus will be an important model plant in horticulture with the generation of germplasm suitable for laboratory operation and the establishment of a regeneration and transformation system.

Ectopic expression of NnPER1, a Nelumbo nucifera 1-cysteine peroxiredoxin antioxidant, enhances seed longevity and stress tolerance in Arabidopsis

Seed longevity, the maintenance of viability during storage, is a major factor for conservation of genetic resources and biodiversity. Seed longevity is an important trait of agriculture crop and is impaired by reactive oxygen species (ROS) during seed desiccation, storage and germination (C. R. Biol., 331, 2008 and 796). Seeds possess a wide range of systems (protection, detoxification, repair) allowing them to survive during storage and to preserve a high germination ability. In many plants, 1-cys peroxiredoxin (1-Cys Prx, also named PER1) is a seed-specific antioxidant which eliminates ROS with cysteine residues. Here we identified and characterized a seed-specific PER1 protein from seeds of sacred lotus (Nelumbo nucifera Gaertn.). Purified NnPER1 protein protects DNA against the cleavage by ROS in the mixed-function oxidation system. The transcription and protein accumulation of NnPER1 increased during seed desiccation and imbibition and under abiotic stress treatment. Ectopic expression of NnPER1 in Arabidopsis enhanced the seed germination ability after controlled deterioration treatment (CDT), indicating that NnPER1 improves seed longevity of transgenic plants. Consistent with the function of NnPER1 on detoxifying ROS, we found that the level of ROS release and lipid peroxidation was strikingly lower in transgenic seeds compared to wild-type with or without CDT. Furthermore, transgenic Arabidopsis seeds ectopic-expressing NnPER1 displayed enhanced tolerance to high temperature and abscisic acid (ABA), indicating that NnPER1 may participate in the thermotolerance and ABA signaling pathway.

Metabolomic and Proteomic Profiles Reveal the Dynamics of Primary Metabolism during Seed Development of Lotus (Nelumbo nucifera)

Sacred lotus (Nelumbo nucifera) belongs to the Nelumbonaceae family. Its seeds are widely consumed in Asian countries as snacks or even medicine. Besides the market value, lotus seed also plays a crucial role in the lotus life cycle. Consequently, it is essential to gain a comprehensive understanding of the development of lotus seed. During its development, lotus seed undergoes cell division, expansion, reserve accumulation, desiccation, and maturation phases. We observed morphological and biochemical changes from 10 to 25 days after pollination (DAP) which corresponded to the reserve synthesis and accumulation phase. The volume of the seed expanded until 20 DAP with the color of the seed coat changing from yellow-green to dark green and gradually fading again. Starch and protein rapidly accumulated from 15 to 20 DAP. To further reveal metabolic adaptation, primary metabolites and proteins profiles were obtained using mass spectrometry based platforms. Metabolites and enzymes involved in sugar metabolism, glycolysis, TCA cycle and amino acid metabolism showed sequential dynamics enabling the clear separation of the different metabolic states during lotus seed development. The integration of the data revealed a highly significant metabolic switch at 15 DAP going through a transition of metabolically highly active tissue to the preparation of storage tissue. The results provide a reference data set for the evaluation of primary metabolism during lotus seed development.

Physiological and biochemical changes during the loss of desiccation tolerance in germinating Adenanthera pavonina L. seeds

ABSTRACT We investigated the loss of desiccation tolerance (DT) in Adenanthera pavonina seeds during germination. Seeds were subjected to imbibition for 0, 24, 36, 48, 60 and 81 h, then dried to their initial moisture content (13%), rehydrated and evaluated for survival (resumption of growth and development of normal seedlings) and membrane system integrity (electrolyte leakage). Embryonic axes of seeds subjected only to imbibition during the same early time periods were used to investigate the electrophoretic patterns of heat-stable proteins and the relative nuclear DNA content. In A. pavonina seeds, DT remained unchanged until 36 h of imbibition (resulting in germination and 82% normal seedlings), after which it was progressively lost, and seeds with a protruded radicle length of 1 mm did not withstand dehydration. The loss of desiccation tolerance could not be related to either membrane damage caused by drying or the resumption of the cell cycle during germination. However, the decrease in heat-stable protein contents observed throughout germination may be related to the loss of DT in A. pavonina seeds.

Thermal-stable proteins of fruit of long-living Sacred Lotus Nelumbo nucifera Gaertn var. China Antique

Single-seeded fruit of the sacred lotus Nelumbo nucifera Gaertn var. China Antique from NE China have viability as long as ~1300 years determined by direct radiocarbon-dating, having a germination rate of 84%. The pericarp, a fruit tissue that encloses the single seeds of Nelumbo, is considered one of the major factors that contribute to fruit longevity. Proteins that are heat stable and have protective function may be equally important to seed viability. We show proteins of Nelumbo fruit that are able to withstand heating, 31% of which remained soluble in the 110°C-treated embryo-axis of a 549-yr-old fruit and 76% retained fluidity in its cotyledons. Genome of Nelumbo is published. The amino-acid sequences of 11 "thermal proteins" (soluble at 100°C) of modern Nelumbo embryo-axes and cotyledons, identified by mass spectrometry, Western blot and bioassay, are assembled and aligned with those of an archaeal-hyperthermophile Methancaldococcus jannaschii (Mj; an anaerobic methanogen having a growth optimum of 85°C) and with five mesophile angiosperms. These thermal proteins have roles in protection and repair under stress. More than half of the Nelumbo thermal proteins (55%) are present in the archaean Mj, indicating their long-term durability and history. One Nelumbo protein-repair enzyme exhibits activity at 100°C, having a higher heat-tolerance than that of Arabidopsis. A list of 30 sequenced but unassembled thermal proteins of Nelumbo is supplemented.