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DELAY OF GERMINATION 1 (AtDOG1) was the first gene identified as dormancy-associated, but its physiological role in germination is far from being understood. Here, an orthologue of AtDOG1 in Sisymbrium officinale (SoDOG1; KM009050) is being reported. Phylogenetically, the SoDOG1 gene is included into the dicotyledonous group together with DOG1 from Arabidopsis thaliana (EF028470), Brassica rapa (AC189537), Lepidium papillosum (JX512183, JX512185) and Lepidium sativum (GQ411192). The SoDOG1 expression peaked at the onset of the silique maturation stage and there was presence of SoDOG1-mRNA in the freshly collected viable dry seed (i.e. AR0). The SoDOG1 transcripts were also found in other organs, such as open and closed flowers and to a lesser degree in roots and stems. We have previously reported in S. officinale seeds in which sensu stricto germination is positively affected by nitrate and both testa and micropylar endosperm ruptures are temporally separated. In dry viable seeds, the SoDOG1-mRNA level in three different after-ripening (AR) status was AR0 ≈ AR7 (optimal AR) < AR27 (optimal AR was almost lost). The presence of nitrate in the AR0 seed imbibition medium markedly decreased the SoDOG1 expression during sensu stricto germination. However, the nitrate stimulated the SoDOG1 expression during imbibition of AR7 compared to AR0. At the early AR0 seed imbibition (3-6 h), exogenous ABA provoked a very strong stimulation of the SoDOG1 expression. AR inhibits ABA-induced SoDOG1 expression during early germination and gibberellins (GA) can partially mimic this AR effect. A view on the integration of all found results in the sensu stricto germination of S. officinale was conducted. [ABSTRACT FROM AUTHOR]

Highlights: [•] After-ripening (AR) overcomes dormancy in Sisymbrium officinale seeds. [•] Nitrate positively affects the AR signaling by increasing the SoNCED5, SoCYP707A2 and SoGA3ox2 expression. [•] Nitrate promotes testa rupture and can substitute to gibberellins (GA) in the presence of paclobutrazol. [•] AR negatively alters the ABA sensitivity in the presence of nitrate. [•] Nitrate promotes sensu-stricto AR and non-AR germination through transcriptional changes of different genes involved in ABA and GA metabolism and signaling. [ABSTRACT FROM AUTHOR]

Endo-β-mannanases ( MAN; EC. 3.2.1.78) catalyze the cleavage of β1→4 bonds in mannan polymers and have been associated with the process of weakening the tissues surrounding the embryo during seed germination. In germinating Arabidopsis thaliana seeds, the most highly expressed MAN gene is At MAN7 and its transcripts are restricted to the micropylar endosperm and to the radicle tip just before radicle emergence. Mutants with a T- DNA insertion in At MAN7 have a slower germination than the wild type. To gain insight into the transcriptional regulation of the At MAN7 gene, a bioinformatic search for conserved non-coding cis-elements (phylogenetic shadowing) within the Brassicaceae MAN7 gene promoters has been done, and these conserved motifs have been used as bait to look for their interacting transcription factors ( TFs), using as a prey an arrayed yeast library from A. thaliana. The basic-leucine zipper TF Atb ZIP44, but not the closely related Atb ZIP11, has thus been identified and its transcriptional activation upon At MAN7 has been validated at the molecular level. In the knock-out lines of Atb ZIP44, not only is the expression of the At MAN7 gene drastically reduced, but these mutants have a significantly slower germination than the wild type, being affected in the two phases of the germination process, both in the rupture of the seed coat and in the breakage of the micropylar endosperm cell walls. In the over-expression lines the opposite phenotype is observed. [ABSTRACT FROM AUTHOR]