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DELAY OF GERMINATION1 (DOG1) - Coggle Diagram
DELAY OF GERMINATION1 (DOG1)
what is it? (Nakabayashi, 2012)
gene
direct role in seed dormancy
identified as a major quantitative trait loci for seed dormancy in a recombinant inbred line...(already in introduction).
key regulator of seed dormancy
dog1 mutants
are completely non-dormant
do not show any obvious pleiotropic phenotypes apart from reduced seed longevity.
DOG1 protein belongs to a small family in Arabidopsis that was recently shown to be conserved in other plant species.
DOG1 homologs have been found in other species such as Lepidium sativum and Brassica rapa and in the monocot rice, Oryza sativa. (Sugimoto et al., 2010)
DOG1 protein levels in freshly harvested dry seeds and the time required for after-ripening.
DOG1 protein becomes modified during seed storage which probably renders it non-functional.
DOG1 functions independent from ABA
presence of both DOG1 and ABA is required for seed dormancy
HYPOTHESIS
DOG1 acts in parallel to ABA signaling and functions as a timer for the release of seed dormancy.
DOG1 mRNA and protein levels show different dynamics
Bentsink et al., 2006-- showed that DOG1 expression can be detected at the beginning of the maturation stage.
these were confirmed via RT-PCR (qRT-PCR) on siliques.
DOG1 transcript levels disappear shortly after seed imbibition.
DOG1 is a very stable protein as it increases at the start of the maturation phase and remains steady after the mid-maturation peak. This was compared against highly dormant genotype Near Isogenic Line DOG1_Cvi (NIL).
Freshly harvested seeds contain low DOG! transcript levels but high DOG protein levels.
DOG1 protein dynamics and after-ripening
DOG1 slightly decreased during dry storage of NIL DOG1 seeds but was still high after 13 weeks of after-ripening when dormancy had already been released.
DOG1 transcripts quickly disappeared after imbibition
DOG1 protein was hardly affected by imbibition in both dormant and after-ripened seeds.
Monitored the dynamics of the transcript and protein levels during imbibition using freshly harvested dormant seeds and after ripened seeds.
Ultimately--
this indicates that germination potential is not correlated with DOG1 protein abundance in after-ripened imbibed seeds.
DOG1 Levels are Up-regulated be a Decrease in Temperature during seed maturation.
Interested in the role of DOG1 in the dormancy response to temperature during seed maturation.
Analysis of DOG1 transcript levels in freshly harvested seeds revealed that seeds matured at 16/14C contained higher DOG1 expression levels compared with seeds that matured at 222/16C in 3 different genotypes.
this means that reduced temperatures during seed maturation enhance DOG1 expression leading to higher DOG1 protein levels and higher dormancy levels.
DOG1 Protein Changes during After-Ripening
Correlation between DOG1 and after-ripening seeds are weaker
the loss of function could be because of an altered protein structure.
Investigated through an analysis of DOG1 protein on a 2D gel.
Indicated that DOG1 protein is altered during the after ripening process.
the shift in isogenic focusing of DOG1 protein during after-ripening has be repeatedly observed in two independent seed batches.
Localization of DOG1 Transcript and Protein
found the vascular tissue of the embryo (mainly)
DOG1 influences the expression of ABA and GA metabolic genes during imbibition
DOG1 is not directly involved in the ABA pathway but de novo ABA synthesis partially contributes to dormancy maintenance in the NIL DOG1.
Among the four genes coding for the enzymes in Arabidopsis, CYP707A2 has been shown to be responsible for degradation of ABA during early imbibition of seeds. Induction of CYP707A1 and CYP707A3 was not observed in NIL DOG1 and dog1-1 (Figure 6). CYP707A2 had similar expression patterns in all three genotypes during imbibition. However, the expression levels in Ler were lower at the beginning of imbibition, while those in dog1-1 were lower at extended imbibition times
We also examined the expression pattern of several GA biosynthetic genes. The level of GA20ox3 transcript was al- ready higher in dry seeds of dog1-1 compared with NIL DOG1 and Ler. Upon imbibition, GA20ox1, 2, and 3 and GA3ox1 and 2 were all induced in dog1-1 from rather early stages onwards.
This induction was not observed in dormant NIL DOG1, suggesting that DOG1 negatively influences GA biosynthesis during imbibition.