Abstract
During the development of the rice female gametophyte (FG, embryo sac), there exists a free-nuclear stage wherein eight nuclei, originating from the same mother cell nucleus, respectively migrate to specific positions to acquire distinct cell identities after cellularization and develop into the egg cell, central cell, or accessory cells. Therefore, this nuclear migration stage is essential for fertilization and rice fertility. How these nuclei can find their own way to exactly move to different predetermined positions and how the two polar nuclei are selected have been intriguing questions for decades. Here, we show that a mitogen-activated protein kinase cascade, composed of OsMEKK2/OsMEKK21, OsMKK6, and OsMPK4, precisely regulates free-nuclear migration and determines the number and identities of polar nuclei. Specifically, OsMKK6 phosphorylates OsMPK4 to restrict nuclear migration at the chalazal pole, ensuring the accurate number and positioning of antipodal cells and polar nuclei. Loss-of-function mutations in OsMKK6 and OsMPK4 result in an excess of polar nuclei at the expense of antipodal cells. Additionally, OsMEKK2 and OsMEKK21 function as upstream regulators, phosphorylating and modulating downstream substrates to control nuclear migration at both poles. This regulation is essential for FG fertility and seed production. Our findings reveal a hierarchical model for the regulation of nuclear migration during embryo sac development and provide valuable insights into how an embryo sac orchestrates the migration of eight nuclei in response to different positional cues, thereby establishing female fertility in rice.
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Claims 6
Claim · model-written summary
The OsMEKK2/OsMEKK21–OsMKK6–OsMPK4 cascade regulates free-nuclear migration and polar-nucleus identity.
- Taxon
- rice
Oryza sativat0 - Gene
- OsMEKK2/OsMEKK21, OsMKK6, and OsMPK4e0
- Outcome
- free-nuclear migration and determines the number and identities of polar nucleie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a mitogen-activated protein kinase cascade, composed of OsMEKK2/OsMEKK21, OsMKK6, and OsMPK4, precisely regulates free-nuclear migration and determines the number and identities of polar nuclei”
t0“rice”
Claim · model-written summary
OsMKK6 phosphorylates OsMPK4 to restrict nuclear migration at the chalazal pole.
- Taxon
- riceOryza sativat0
- Gene
- OsMKK6e0
- Outcome
- nuclear migration at the chalazal polee0
- Qualifier
- phosphorylates OsMPK4e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“OsMKK6 phosphorylates OsMPK4 to restrict nuclear migration at the chalazal pole”
t0“rice”
Claim · model-written summary
OsMKK6 loss of function produced excess polar nuclei at the expense of antipodal cells.
- Taxon
- riceOryza sativat0
- Gene
- OsMKK6e0
- Outcome
- polar nucleie0
- Direction
- excesse0
- Qualifier
- at the expense of antipodal cellse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Loss-of-function mutations in OsMKK6 and OsMPK4 result in an excess of polar nuclei at the expense of antipodal cells”
t0“rice”
Claim · model-written summary
OsMPK4 loss of function produced excess polar nuclei at the expense of antipodal cells.
- Taxon
- riceOryza sativat0
- Gene
- OsMPK4e0
- Outcome
- polar nucleie0
- Direction
- excesse0
- Qualifier
- at the expense of antipodal cellse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Loss-of-function mutations in OsMKK6 and OsMPK4 result in an excess of polar nuclei at the expense of antipodal cells”
t0“rice”
Claim · model-written summary
OsMEKK2 and OsMEKK21 phosphorylate downstream substrates to control nuclear migration at both poles.
- Taxon
- riceOryza sativat0
- Gene
- OsMEKK2 and OsMEKK21e0
- Outcome
- nuclear migration at both polese0
- Qualifier
- phosphorylating and modulating downstream substratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“OsMEKK2 and OsMEKK21 function as upstream regulators, phosphorylating and modulating downstream substrates to control nuclear migration at both poles”
t0“rice”
Claim · model-written summary
This cascade regulation is essential for female gametophyte fertility and seed production.
- Taxon
- riceOryza sativat0
- Outcome
- FG fertility and seed productione0
- Qualifier
- This regulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This regulation is essential for FG fertility and seed production”
t0“rice”