Seed dormancy is one of the most crucial process transitions in a plant's life cycle. Its timing is tightly controlled by the expression level of the Delay of Germination 1 gene (DOG1). DOG1 is the major quantitative trait locus for seed dormancy in Arabidopsis and has been shown to control dormancy in many other plant species. This is reflected by the evolutionary conservation of the functional short alternatively polyadenylated form of the DOG1 mRNA. Notably, the 3′ region of DOG1, including the last exon that is not included in this transcript isoform, shows a high level of conservation at the DNA level, but the encoded polypeptide is poorly conserved. Here, we demonstrate that this region of DOG1 contains a promoter for the transcription of a noncoding antisense RNA, asDOG1, that is 5′ capped, polyadenylated, and relatively stable. This promoter is autonomous and asDOG1 has an expression profile that is different from known DOG1 transcripts. Using several approaches we show that asDOG1 strongly suppresses DOG1 expression during seed maturation in cis, but is unable to do so in trans. Therefore, the negative regulation of seed dormancy by asDOG1 in cis results in allele-specific suppression of DOG1 expression and promotes germination. Given the evolutionary conservation of the asDOG1 promoter, we propose that this cis-constrained noncoding RNA-mediated mechanism limiting the duration of seed dormancy functions across the Brassicaceae.seed dormancy | DOG1 gene | cis-acting ncRNA | antisense transcript P lants have evolved elaborate adaptation mechanisms to cope with unexpected and rapid changes in their natural environment (1). The division of the plant life cycle into consecutive developmental phases can be viewed as one such mechanism. This compartmentalization allows plants to focus their resources on particular tasks. The most pronounced developmental phases in plant development are seed dormancy, the juvenile phase, vegetative growth, flowering, and senescence (2). The transition between each successive phase has to be tightly controlled and aligned with the plant's internal metabolic state and external conditions.Seeds are characterized by their remarkable ability to withstand harsh environmental conditions (3). This is in part because of a seed dormancy mechanism that imposes a block on the ability of seeds to sense permissive conditions and initiate germination (4, 5). This mechanism allows seeds to temporarily bypass favorable conditions to germinate in an environment that will support the entire plant life cycle. Seed dormancy is under strong evolutionary selection because the improper timing of germination often results in immediate death (6). In addition, from an agronomical point of view, seed dormancy has been a subject of intensive selection, because on the one hand strong dormancy leads to uneven germination, but on the other hand weak dormancy may result in preharvest sprouting because of germination on the mother plant (7).An analysis of seed dormancy variability among Arabidopsis thaliana ac...

ORCID IDs: 0000-0001-7449-8081 (M.C.); 0000-0001-8764-6370 (F.L.).DOG1 (Delay of Germination 1) is a key regulator of seed dormancy in Arabidopsis (Arabidopsis thaliana) and other plants. Interestingly, the C terminus of DOG1 is either absent or not conserved in many plant species. Here, we show that in Arabidopsis, DOG1 transcript is subject to alternative polyadenylation. In line with this, mutants in RNA 39 processing complex display weakened seed dormancy in parallel with defects in DOG1 proximal polyadenylation site selection, suggesting that the short DOG1 transcript is functional. This is corroborated by the finding that the proximally polyadenylated short DOG1 mRNA is translated in vivo and complements the dog1 mutant. In summary, our findings indicate that the short DOG1 protein isoform produced from the proximally polyadenylated DOG1 mRNA is a key player in the establishment of seed dormancy in Arabidopsis and characterizes a set of mutants in RNA 39 processing complex required for production of proximally polyadenylated functional DOG1 transcript.

ATP-dependent chromatin remodeling complexes are important regulators of gene expression in Eukaryotes. In plants, SWI/SNF-type complexes have been shown critical for transcriptional control of key developmental processes, growth and stress responses. To gain insight into mechanisms underlying these roles, we performed whole genome mapping of the SWI/SNF catalytic subunit BRM in Arabidopsis thaliana, combined with transcript profiling experiments. Our data show that BRM occupies thousands of sites in Arabidopsis genome, most of which located within or close to genes. Among identified direct BRM transcriptional targets almost equal numbers were up- and downregulated upon BRM depletion, suggesting that BRM can act as both activator and repressor of gene expression. Interestingly, in addition to genes showing canonical pattern of BRM enrichment near transcription start site, many other genes showed a transcription termination site-centred BRM occupancy profile. We found that BRM-bound 3΄ gene regions have promoter-like features, including presence of TATA boxes and high H3K4me3 levels, and possess high antisense transcriptional activity which is subjected to both activation and repression by SWI/SNF complex. Our data suggest that binding to gene terminators and controlling transcription of non-coding RNAs is another way through which SWI/SNF complex regulates expression of its targets.

Plants have developed multiple strategies to sense the external environment and to adapt growth accordingly. () is a major quantitative trait locus (QTL) for seed dormancy strength in that is reported to be expressed exclusively in seeds. is extensively regulated, with an antisense transcript () suppressing its expression in seeds. Here, we show that shows high levels in mature plants where it suppresses expression under standard growth conditions. Suppression is released by shutting down antisense transcription, which is induced by the plant hormone abscisic acid (ABA) and drought. Loss of results in constitutive high-level expression, conferring increased drought tolerance, while inactivation of causes enhanced drought sensitivity. The unexpected role of in environmental adaptation of mature plants is separate from its function in seed dormancy regulation. The requirement of to respond to ABA and drought demonstrates that antisense transcription is important for sensing and responding to environmental changes in plants.