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Independent and interactive effects of DOF affecting germination 1 (DAG1) and the Della proteins GA insensitive (GAI) and Repressor of ga1-3 (RGA) in embryo development and seed germination.

Boccaccini A, Santopolo S, Capauto D, Lorrai R, Minutello E, Belcram K, Palauqui JC, Costantino P, Vittorioso P - BMC Plant Biol. (2014)

Bottom Line: Among others, PIL5 induces the expression of the genes encoding the two DELLA proteins GA INSENSITIVE 1 (GAI) and REPRESSOR OF ga1-3 (RGA).In addition, the germination properties of the dag1rga28 double mutant are different from those of the dag1 and rga28 single mutants, suggesting that RGA and DAG1 act in independent branches of the PIL5-controlled germination pathway.Surprisingly, the dag1gai-t6 double mutant proved embryo-lethal, suggesting an unexpected involvement of (a possible complex between) DAG1 and GAI in embryo development.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: The transcription factor DOF AFFECTING GERMINATION1 (DAG1) is a repressor of seed germination acting downstream of the master repressor PHYTOCROME INTERACTING FACTOR3-LIKE 5 (PIL5). Among others, PIL5 induces the expression of the genes encoding the two DELLA proteins GA INSENSITIVE 1 (GAI) and REPRESSOR OF ga1-3 (RGA).

Results: Based on the properties of gai-t6 and rga28 mutant seeds, we show here that the absence of RGA severely increases dormancy, while lack of GAI only partially compensates RGA inactivation. In addition, the germination properties of the dag1rga28 double mutant are different from those of the dag1 and rga28 single mutants, suggesting that RGA and DAG1 act in independent branches of the PIL5-controlled germination pathway. Surprisingly, the dag1gai-t6 double mutant proved embryo-lethal, suggesting an unexpected involvement of (a possible complex between) DAG1 and GAI in embryo development.

Conclusions: Rather than overlapping functions as previously suggested, we show that RGA and GAI play distinct roles in seed germination, and that GAI interacts with DAG1 in embryo development.

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Embryo phenotype ofdag1,gai-t6and of F1 plants derived from thedag1x gai-t6cross. (A-J) Transversal and longitudinal section of wild-type (Ws-4 and Col-0) (A, B, E, F), gai-t6(C, D), dag1(G, H), and F1 embryos at globular stage (I, J). (K, L) Transversal and longitudinal section of F2 embryos at heart stage. (M-R) Longitudinal and 3D vizualisation of wild-type (M-O) and F1 embryos at transition stage (P-R). F1 is referred to embryos from F1 plants derived from the cross dag1 × gai-t6. Green arrows indicate correct division plane. Red arrows indicate incorrect division plane. Black arrows indicate sagging of the embryo. Scale bar 10 μm.
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Figure 5: Embryo phenotype ofdag1,gai-t6and of F1 plants derived from thedag1x gai-t6cross. (A-J) Transversal and longitudinal section of wild-type (Ws-4 and Col-0) (A, B, E, F), gai-t6(C, D), dag1(G, H), and F1 embryos at globular stage (I, J). (K, L) Transversal and longitudinal section of F2 embryos at heart stage. (M-R) Longitudinal and 3D vizualisation of wild-type (M-O) and F1 embryos at transition stage (P-R). F1 is referred to embryos from F1 plants derived from the cross dag1 × gai-t6. Green arrows indicate correct division plane. Red arrows indicate incorrect division plane. Black arrows indicate sagging of the embryo. Scale bar 10 μm.

Mentions: We then analyzed the phenotype of F2 embryos and checked for additional phenotypes compared to wild-type and single mutants. In wild-type, dag1 and gai-t6 single mutants, transversal division of basal vascular cells at globular stage led to asymmetric cells (Figure 5A,C,E,G). In contrast, some F2 embryos displayed longitudinal divisions (Figure 5I,K), thus altering the radial symmetry of the embryo axis (Figure 5J,L) observed in control plants (Figure 5B,D,F,H). An additional phenotype was observed at the transition stage where individuals of the F2 embryos showed aberrant triangular shape, as highlighted by the arrow (Figure 5P) and also shown in the 3D image (Figure 5Q,R) compared to wild-type embryos (Figure 5M-O). Interestingly, a small percentage of dag1 embryos also showed similar phenotypes (Figure 6).


Independent and interactive effects of DOF affecting germination 1 (DAG1) and the Della proteins GA insensitive (GAI) and Repressor of ga1-3 (RGA) in embryo development and seed germination.

Boccaccini A, Santopolo S, Capauto D, Lorrai R, Minutello E, Belcram K, Palauqui JC, Costantino P, Vittorioso P - BMC Plant Biol. (2014)

Embryo phenotype ofdag1,gai-t6and of F1 plants derived from thedag1x gai-t6cross. (A-J) Transversal and longitudinal section of wild-type (Ws-4 and Col-0) (A, B, E, F), gai-t6(C, D), dag1(G, H), and F1 embryos at globular stage (I, J). (K, L) Transversal and longitudinal section of F2 embryos at heart stage. (M-R) Longitudinal and 3D vizualisation of wild-type (M-O) and F1 embryos at transition stage (P-R). F1 is referred to embryos from F1 plants derived from the cross dag1 × gai-t6. Green arrows indicate correct division plane. Red arrows indicate incorrect division plane. Black arrows indicate sagging of the embryo. Scale bar 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4222566&req=5

Figure 5: Embryo phenotype ofdag1,gai-t6and of F1 plants derived from thedag1x gai-t6cross. (A-J) Transversal and longitudinal section of wild-type (Ws-4 and Col-0) (A, B, E, F), gai-t6(C, D), dag1(G, H), and F1 embryos at globular stage (I, J). (K, L) Transversal and longitudinal section of F2 embryos at heart stage. (M-R) Longitudinal and 3D vizualisation of wild-type (M-O) and F1 embryos at transition stage (P-R). F1 is referred to embryos from F1 plants derived from the cross dag1 × gai-t6. Green arrows indicate correct division plane. Red arrows indicate incorrect division plane. Black arrows indicate sagging of the embryo. Scale bar 10 μm.
Mentions: We then analyzed the phenotype of F2 embryos and checked for additional phenotypes compared to wild-type and single mutants. In wild-type, dag1 and gai-t6 single mutants, transversal division of basal vascular cells at globular stage led to asymmetric cells (Figure 5A,C,E,G). In contrast, some F2 embryos displayed longitudinal divisions (Figure 5I,K), thus altering the radial symmetry of the embryo axis (Figure 5J,L) observed in control plants (Figure 5B,D,F,H). An additional phenotype was observed at the transition stage where individuals of the F2 embryos showed aberrant triangular shape, as highlighted by the arrow (Figure 5P) and also shown in the 3D image (Figure 5Q,R) compared to wild-type embryos (Figure 5M-O). Interestingly, a small percentage of dag1 embryos also showed similar phenotypes (Figure 6).

Bottom Line: Among others, PIL5 induces the expression of the genes encoding the two DELLA proteins GA INSENSITIVE 1 (GAI) and REPRESSOR OF ga1-3 (RGA).In addition, the germination properties of the dag1rga28 double mutant are different from those of the dag1 and rga28 single mutants, suggesting that RGA and DAG1 act in independent branches of the PIL5-controlled germination pathway.Surprisingly, the dag1gai-t6 double mutant proved embryo-lethal, suggesting an unexpected involvement of (a possible complex between) DAG1 and GAI in embryo development.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: The transcription factor DOF AFFECTING GERMINATION1 (DAG1) is a repressor of seed germination acting downstream of the master repressor PHYTOCROME INTERACTING FACTOR3-LIKE 5 (PIL5). Among others, PIL5 induces the expression of the genes encoding the two DELLA proteins GA INSENSITIVE 1 (GAI) and REPRESSOR OF ga1-3 (RGA).

Results: Based on the properties of gai-t6 and rga28 mutant seeds, we show here that the absence of RGA severely increases dormancy, while lack of GAI only partially compensates RGA inactivation. In addition, the germination properties of the dag1rga28 double mutant are different from those of the dag1 and rga28 single mutants, suggesting that RGA and DAG1 act in independent branches of the PIL5-controlled germination pathway. Surprisingly, the dag1gai-t6 double mutant proved embryo-lethal, suggesting an unexpected involvement of (a possible complex between) DAG1 and GAI in embryo development.

Conclusions: Rather than overlapping functions as previously suggested, we show that RGA and GAI play distinct roles in seed germination, and that GAI interacts with DAG1 in embryo development.

Show MeSH
Related in: MedlinePlus