Dry seed transcriptome differences associated with relief of sly1-2 seed dormancy through after-ripening or overexpression of the gibberellin-receptor GID1b

Plant embryos can survive years in a desiccated, quiescent state within seeds. In many species, seeds are dormant and unable to germinate at maturity. They acquire the capacity to germinate through a period of dry storage called after-ripening (AR), a biological process that occurs at 5-15% moisture when most metabolic processes cease. Because stored transcripts will be among the first proteins translated upon water uptake, they likely impact germination potential. Transcriptome changes associated with the increased seed dormancy of the GA-insensitive <i>sly1-2</i> mutant, and with dormancy loss through <i>sly1-2</i> after-ripening or constitutive overexpression of the GA receptor (GID1b) were characterized in dry seeds. This experiment used the same seed batches as a previous experiment (E-MTAB-4782) to characterize transcriptional changes associated with the increased seed dormancy and dormancy loss in imbibing seeds. The <i>SLY1</i> gene encodes the F-box subunit of an SCF E3 ubiquitin ligase needed for GA-triggered proteolysis of DELLA repressors of seed germination. In the <i>sly1-2</i> mutant, GA-directed DELLA proteolysis cannot occur leading to DELLA protein accumulation and increased dormancy. <i>sly1-2</i> mutant seeds are fully dormant at 2 weeks of dry storage (0% germination), but germinate well with very long after-ripening (51% germination after 19 months). <i>sly1-2</i> seed germination can also be rescued by overexpression of the GA receptor, <i>GA-INSENSITIVE DWARF1b</i> (<i>GID1b-OE</i>), which resulted in 74% germination at 2 weeks of dry storage. In this experiment, we sampled dry seeds of wild-type L<i>er</i> at 2 weeks of dry storage (non-dormant), dormant <i>sly1-2</i> (2 weeks of dry storage; <i>sly1-2</i>(D)), long after-ripened <i>sly1-2</i> (non-dormant, 19 months of dry storage; <i>sly1-2</i>(AR)), and <i>sly1-2 GID1b-OE</i> (non-dormant, 2 weeks of dry storage). This experimental design allowed comparison between these transcriptomes in dry seeds to determine if dry seed stored mRNA differences contribute to the dormancy phenotypes observed once seeds are imbibed. Seeds for L<i>er</i> wt, <i>sly1-2</i>(D), and <i>sly1-2 GID1b-OE</i> were grown alongside each other under the same conditions and after-ripened for 2 weeks. Seeds from <i>sly1-2</i>(AR) were grown under the same conditions in advance of the other lines to allow for the long after-ripening requirement. RNA was extracted using a phenol-chloroform-based extraction from three biological replicates per treatment.

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