Embryo sac development relies on symplastic signals from ovular integuments in Arabidopsis

Abstract

SUMMARYOvules are female reproductive organs of angiosperms, consisting of sporophytic integuments surrounding female gametophytes, that is, embryo sacs. Synchronization between integument growth and embryo sac development requires intracellular communication. However, signaling routes through which cells of the two generations communicate are unclear. We report that symplastic signals through plasmodesmata (PDs) of integuments are critical for the development of female gametophytes. Genetic interferences of PD biogenesis either by functional loss of CHOLINE TRANSPORTER‐LIKE1 (CTL1) or by integument‐specific expression of a mutated CALLOSE SYNTHASE 3 (cals3m) compromised PD formation in integuments and reduced fertility. Close examination of pINO:cals3m or ctl1 ovules indicated that female gametophytic development was either arrested at various stages after the formation of functional megaspores. In both cases, defective ovules could not attract pollen tubes, leading to the failure of fertilization. Results presented here demonstrate a key role of the symplastic route in sporophytic control of female gametophytic development.

Autophagy-mediated degradation of integumentary tapetum is critical for embryo pattern formation

“…It has been speculated that this tissue serves multiple roles in seed development, such as providing the necessary nutrients and supporting embryo and endosperm development, based on its strategic location and cytological characteristics. Consistent with this notion, a recent study revealed the significance of symplastic signals through plasmodesmata of integuments for the pre-fertilization development of the embryo sac 55 . In addition, another recent research demonstrated that micropylar integumentary-tapetum-generated gibberellin serves as a maternal signal regulating PCD initiation in the embryonic suspensor through the NtGID1-NtCRF1-NtCYS-NtCP14 signaling cascade 56 .…”