Biochemical Profile of the Soybean Seed Embryonic Axis and Its Changes during Accelerated Aging

Insights into mechanisms of seed longevity in soybean: a review

Soybean, a crop of international importance, is challenged with the problem of seed longevity mainly due to its genetic composition and associated environmental cues. Soybean's fragile seed coat coupled with poor DNA integrity, ribosomal dysfunction, lipid peroxidation and poor antioxidant system constitute the rationale for fast deterioration. Variability among the genotypes for sensitivity to field weathering contributed to their differential seed longevity. Proportion and density of seed coat, glassy state of cells, calcium and lignin content, pore number, space between seed coat and cotyledon are some seed related traits that are strongly correlated to longevity. Further, efficient antioxidant system, surplus protective proteins, effective nucleotide and protein repair systems and free radical scavenging mechanisms also contributed to the storage potential of soybean seeds. Identification of molecular markers and QTLs associated with these mechanisms will pave way for enhanced selection efficiency for seed longevity in soybean breeding programs. This review reflects on the morphological, biochemical and molecular bases of seed longevity along with pointers on harvest, processing and storage strategies for extending vigour and viability in soybean.

Full-Length Transcriptome Sequencing Reveals the Molecular Mechanism of Metasequoia glyptostroboides Seed Responding to Aging

Metasequoia glyptostroboides, Hu and W. C. Cheng, as the only surviving relict species of the Taxodiaceae Metasequoia genus, is a critically endangered and protected species in China. There is a risk of extinction due to the low vigor of M. glyptostroboides seeds, and the physiological mechanism of seed aging in M. glyptostroboides is not yet clear. In order to investigate the physiological and molecular mechanisms underlying the aging process of M. glyptostroboides seeds, we analyzed the antioxidant system and transcriptome at 0, 2, 4, 6, and 8 days after artificial accelerated aging treatment at 40 °C and 100% relative humidity. It was found that the germination percentage of fresh dried M. glyptostroboides seeds was 54 ± 5.29%, and significantly declined to 9.33 ± 1.88% after 6 days of aging, and then gradually decreased until the seed died on day 8. Superoxide dismutase (SOD) activity, ascorbic acid (AsA), glutathione (GSH) content and superoxide anion (O₂^·-) content and production rate significantly decreased, while malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content and glutathione peroxidase (GPX) and catalase (CAT) activity gradually increased during the aging process. A total of 42,189 unigenes were identified in the whole transcriptome, and 40,446 (95.86%) unigenes were annotated in at least one protein database. A total of 15,376 differentially expressed genes (DEGs) were obtained; KEGG enrichment analysis results revealed that seed aging may be mainly involved in the protein-processing pathways in endoplasmic reticulum, oxidative phosphorylation, and ascorbate and aldarate metabolism. Weighted gene co-expression network analysis (WGCNA) revealed that the dark magenta, orange, and medium purple modules were highly correlated with physiological indicators such as SOD, CAT, and GSH and further identified 40 hub genes such as Rboh, ACO, HSF, and CML as playing important roles in the antioxidant network of M. glyptostroboides seeds. These findings provide a broader perspective for studying the regulatory mechanism of seed aging and a large number of potential target genes for the breeding of other endangered gymnosperms.

Morphological, physiological and biochemical response of Lallemantia species to elevated temperature and light duration during seed development

Seed weight, storability, and germinability can depend on maternal plant's environment. However, there is slight information about the effect of light and temperature on seed quality of Lallemantia species. The purpose of this research was to determine the properties of physio-biochemical of maternal plant, seed quality, and seed chemical composition of Lallemantia species (Lallemantia iberica and Lallemantia royleana) under temperature (15 °C, 25 °C, and 35 °C) and photoperiod (8 hd^-1, 16 hd^-1, and 24 hd^-1) maternal plants environment. Increasing temperature and photoperiod caused a reduction in leaf chlorophyll, stomatal movement, total soluble sugar, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzymes activities, and an increment in malondialdehyde (MDA) and hydrogen peroxide (H2O2) content of seeds. However, the highest weight, germination, vigor index, and longevity, seed chemical compositions were obtained in offspring which matured under 25 °C for 16 hd^-1. The highest germination, oil, and relative percentage of fatty acids (oleic acid (OA), linoleic acid (LA), and linolenic acid (LNA)) were obtained in L. iberica seeds. On the contrary, longevity, mucilage, and sucrose were more abundant in L. royleana seeds. Overall, this research has clearly shown that temperature and light quality and quantity of maternal plant's environment have an immensely effect on producing of seeds with high-quality. However, it is necessary to investigate the impact of the epigenetic mechanisms of the maternal plant on the offspring in future studies.