Kranner, I. | bioRxiv Science

bioRxiv2021

Comparative analysis of wild type accessions reveals novel determinants of Arabidopsis seed longevity

Understanding the genetic factors involved in seed longevity is of paramount importance in agricultural and ecological contexts. The polygenic nature of this trait suggests that many of them remain undiscovered. Here, we exploited the contrasting seed longevity found amongst wild type Arabidopsis thaliana accessions to further understand this phenomenon. Concentrations of the antioxidant glutathione were consistently higher in longer-lived than shorter-lived accessions, supporting that redox poise plays a prominent role in seed longevity. However, high seed permeability, normally associated with shorter longevity, is also present in accessions with longer seed longevity. Transcriptome analysis indicated that the detrimental effect on longevity caused by seed coat permeability may be counterbalanced by higher levels of specific mRNAs stored in dry seed, particularly those of heat-shock proteins. Indeed, reverse genetics demonstrated that heat-shock factors HSF1A and 1B contributed to longevity. Furthermore, loss-of-function mutants of RNA-binding proteins, such as the stress-granule zinc-finger protein TZF9, or the spliceosome subunits MOS4 or MAC3A/MAC3B, extended seed longevity, positioning RNA as a novel player in the regulation of seed viability. mRNAs of proteins with putative relevance to longevity were also abundant in shorter-lived accessions, reinforcing the idea that resistance to ageing is determined by multiple factors.

plant biology↗

bioRxiv2020

Cytoplasmic physical state governs the influence of oxygen on Pinus densiflora seed ageing

During desiccation, the cytoplasm of orthodox seeds solidifies in a glass with highly restricted diffusion and molecular mobility, which extend longevity. Temperature and moisture determine seed cellular physical state, and oxygen can promote deteriorative reactions of seed ageing. However, whether seed physical state affects O2-mediated biochemical reactions during ageing remains unknown. Here, we answered this question using oil-rich Pinus densiflora seeds aged by controlled deterioration (CD) at 45 {degrees}C and distinct relative humidities (RHs), resulting in a glassy (9 and 33% RH) or fluid (64 and 85% RH) cytoplasm. Regardless of CD regimes, the cellular lipid domain remained always fluid. Hypoxia (0.4% O2) prevented seed deterioration only in the glassy state, limiting non-enzymatic lipid peroxidation, consumption of antioxidants (glutathione, tocopherols) and unsaturated fatty acids, accompanied by decreased lipid melt enthalpy and lower concentrations of aldehydes and reactive electrophile species (RES). In contrast, a fluid cytoplasm promoted faster seed deterioration and enabled the resumption of enzymatic activities implicated in glutathione metabolism and RES detoxification, regardless of O2 availability. Furthermore, seeds stored under dry/cold seed bank conditions showed biochemical profiles similar to those of CD-aged seeds with glassy cytoplasm under normoxia. These findings are discussed in the context of germplasm management. Highlightlipid peroxidation occurred during seed ageing in the glassy state and, like viability loss, could be prevented by hypoxia. Seeds with fluid cytoplasm aged faster and irrespective of oxygen availability.

plant biology↗