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DELAY OF GERMINATION-1 (DOG1), is a master regulator of primary dormancy (PD) that acts in concert with ABA to delay germination. The ABA and DOG1 signaling pathways converge since DOG1 requires protein phosphatase 2C (PP2C) to control PD. DOG1 enhances ABA signaling through its binding to PP2C ABA HYPERSENSITIVE GERMINATION (AHG1/AHG3). DOG1 suppresses the AHG1 action to enhance ABA sensitivity and impose PD. To carry out this suppression, the formation of DOG1-heme complex is essential. The binding of DOG1-AHG1 to DOG1-Heme is an independent processes but essential for DOG1 function. The quantity of active DOG1 in mature and viable seeds is correlated with the extent of PD. Thus, dog1 mutant seeds, which have scarce endogenous ABA and high gibberellin (GAs) content, exhibit a non-dormancy phenotype. Despite being studied extensively in recent years, little is known about the molecular mechanism underlying the transcriptional regulation of DOG1 . However, it is well-known that the physiological function of DOG1 is tightly regulated by a complex array of transformations that include alternative splicing, alternative polyadenylation, histone modifications, and a cis -acting antisense non-coding transcript ( asDOG1 ). The DOG1 becomes modified (i.e., inactivated) during seed after-ripening (AR), and its levels in viable seeds do not correlate with germination potential. Interestingly, it was recently found that the transcription factor (TF) bZIP67 binds to the DOG1 promoter. This is required to activate DOG1 expression leading to enhanced seed dormancy. On the other hand, seed development under low-temperature conditions triggers DOG1 expression by increasing the expression and abundance of bZIP67. Together, current data indicate that DOG1 function is not strictly limited to PD process, but that it is also required for other facets of seed maturation, in part by also interfering with the ethylene signaling components. Otherwise, since DOG1 also affects other processes such us flowering and drought tolerance, the approaches to understanding its mechanism of action and control are, at this time, still inconclusive.

Main Conclusion: Mannans but not endo-β-mannanases are mainly found in the mucilage layer of two Brassicaceae seeds. Nonetheless, mannanase mobilization from inner to outer seed layers cannot be ruled out. The contribution of endo-β-mannanase (MAN) genes to the germination of the wild-type Sisymbrium officinale and cultivated Brassica rapa (Brassicaceae) species has been explored. In both species, mannans have been localized to the imbibed external seed coat layer (mucilage) by fluorescence immunolocalization and MAN enzymatic activity increases in seeds as imbibition progresses, reaching a peak before 100% germination is achieved. The MAN gene families have been annotated and the expression of their members analyzed in vegetative and reproductive organs. In S. officinale and B. rapa, MAN2, MAN5, MAN6, and MAN7 transcripts accumulate upon seed imbibition. SoMAN7 is the most expressed MAN gene in S. officinale germinating seeds, as occurs with its ortholog in Arabidopsis thaliana, but in B. rapa, the most abundant transcripts are BrMAN2 and BrMAN5. These genes (MAN2, MAN5, MAN6, and MAN7) are localized, by mRNA in situ hybridization, to the micropylar at the endosperm layer and to the radicle in S. officinale, but in B. rapa, these mRNAs are faintly found to the micropylar living seed coat layer and are mainly present at the radicle tip and the vascular bundles. If the domestication process undergone by B. rapa is responsible for these different MAN expression patterns, upon germination remains to be elucidated. Since mannans and MAN genes are not spatially distributed in the same seed tissues, a movement of MAN enzymes that are synthesized with typical signal peptides from the embryo tissues to the mucilage layer (via apoplastic space) is necessary for the mannans to be hydrolyzed.

The mature silique of turnip-tops (Brassica rapa L. cv. Rapa) contains seeds that are heterogeneous in colour. From these seeds, we have selected three homogeneous lots: black (B), dark brown (DB) and light brown (LB). The dry seeds of these lots contained different levels of free and conjugated 1-aminocyclopropane-1-carboxylic acid (ACC), polyamines (PA) and ABA, the levels of the latter being inversely related to the germinative capacity. The water uptake (WU) rate was much faster in LB seeds than in B. This fact was probably related to the breaking of the seed coat, the speed of which was B >> DB > LB. The ABA, spermidine (Spd) and spermine (Spm) contents decreased in the seeds during germination, whereas the putrescine (Put) levels rose sharply (B > DB > LB). For the first time in seeds, heterogeneity is reported with respect to ethylene sensitivity and synthesis. Whereas exogenous ethylene did not alter the percentage of germination in lot B, germination was higher in DB and LB (LB>> DB) in the presence of ethylene. The final step of the ethylene pathway was altered concomitantly with this change in germinating capacity, affecting the levels of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC), ACC, ACC-oxidase (ACO) and ethylene production. The gene BrACO1, recently characterised by us, is expressed differently in the three seed lots, particularly in the LB, where little transcription occurs. Finally, ethylene inhibits Put, Spd and Spm levels at different intensities in the three lots. The results point towards variation in the channelling of ACC towards synthesis of ethylene and / or PA, caused by the heterogeneity.