Abstract
Seeds exist in the vulnerable state of being unable to repair the chemical degradation all organisms suffer, which slowly ages seeds and eventually results in death. Proposed seed aging mechanisms involve all classes of biological molecules, and degradation of total RNA has been detected contemporaneously with viability loss in dry-stored seeds. To identify changes specific to mRNA, we examined the soybean (Glycine max) seed transcriptome, using new, whole-molecule sequencing technology. We detected strong evidence of transcript fragmentation in 23-year-old, compared with 2-year-old, seeds. Transcripts were broken non-specifically, and greater fragmentation occurred in longer transcripts, consistent with the proposed mechanism of molecular fission by free radical attack at random bases. Seeds died despite high integrity of short transcripts, indicating that functions encoded by short transcripts are not sufficient to maintain viability. This study provides an approach to probe the asymptomatic phase of seed aging, namely by quantifying transcript degradation as a function of storage time.
Highlights
Seeds have a limited lifespan that depends on species, growth conditions, and storage environment
This study provides an approach to probe the asymptomatic phase of seed aging, namely by quantifying transcript degradation as a function of storage time
We found that integrity of total RNA, measured using RNA integrity number (RIN), within dry-stored seeds is strongly and positively correlated with germination potential (Fleming et al, 2017)
Summary
Seeds have a limited lifespan that depends on species, growth conditions, and storage environment. The inevitable death of dry-stored seeds arises from accumulation of molecular damage, non-enzymatic oxidation of proteins, lipids, and nucleic acids (Oracz et al, 2007; Terskikh et al, 2008; Rajjou et al, 2008; Kranner et al, 2011). Assessing sub-lethal damage requires a different approach. The inherent fragility of RNA makes it a promising target for quantifying sub-lethal damage, and automated RNA integrity assays, such as the RNA integrity number (RIN), facilitate this approach (Schroeder et al, 2006; Fleming et al, 2017). We found that integrity of total RNA, measured using RIN, within dry-stored seeds is strongly and positively correlated with germination potential (Fleming et al, 2017). RIN mainly reflects integrity of rRNA, and here we explore mRNA as a potentially more sensitive marker of aging
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