Abstract
Angiosperm seed development is a paradigm of tissue cross-talk. Proper seed formation requires spatial and temporal coordination of the fertilization products – embryo and endosperm – and the surrounding seed coat maternal tissue. In early Arabidopsis seed development, all seed integuments were thought to respond homogenously to endosperm growth. Here, we show that the sub-epidermal integument cell layer has a unique developmental program. We characterized the cell patterning of the sub-epidermal integument cell layer, which initiates a previously uncharacterized extra cell layer, and identified TRANSPARENT TESTA 16 and SEEDSTICK MADS box transcription factors as master regulators of its polar development and cell architecture. Our data indicate that the differentiation of the sub-epidermal integument cell layer is insensitive to endosperm growth alone and to the repressive mechanism established by FERTILIZATION INDEPENDENT ENDOSPERM and MULTICOPY SUPPRESSOR OF IRA1 Polycomb group proteins. This work demonstrates the different responses of epidermal and sub-epidermal integument cell layers to fertilization.
Highlights
In angiosperms, seed development starts with the double fertilization of the egg and central cell in the ovule that leads to the formation of embryo and endosperm, respectively
The FERTILIZATION INDEPENDENT ENDOSPERM (FIE) and MULTICOPY SUPPRESSOR OF IRA1 (MSI1) FERTILIZATION INDEPENDENT SEED (FIS) Polycomb group (PcG) proteins act sporophytically to repress the differentiation of the integuments (Roszak and Köhler, 2011)
Endosperm and seed coat coordinate their growth through a cross-talk signaling pathway (Ingram, 2010) that was first identified in the study of the maternally acting TRANSPARENT TESTA GLABRA 2 (TTG2) and zygotically acting HAIKU (IKU) genes
Summary
In angiosperms, seed development starts with the double fertilization of the egg and central cell in the ovule that leads to the formation of embryo and endosperm, respectively. In Arabidopsis, ovule primordia are composed of three functional domains: the funiculus, which transports nutrients from the mother plant; the chalaza, which initiates two integuments; and the nucellus, which gives rise to the female gametophyte Both inner (ii) and outer (oi) integuments are composed of two epidermal cell layers (ii, ii2, oi and oi2) which grow by anticlinal cell divisions. Gcs pollen tube content induces full differentiation of the integuments of medea FIS PcG mutant ovules, which undergo fertilization-independent proliferation of the central cell. These data suggest that pollen tube rupture and not fertilization enables the central cell to initiate the signaling pathway that leads to differentiation of the seed coat. Both ttg and iku mutants show premature arrest of endosperm development and reduced seed size, indicating that the developmental interaction between seed coat and endosperm orchestrates early seed growth with limited embryo contribution (Garcia et al, 2005)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
