Paternal Control of Embryonic Patterning in <i>Arabidopsis thaliana</i>

TLDR

The YODA MAPK pathway drives zygote elongation and suspensor formation, while SSP transcripts are produced in mature pollen but are not translated. The study aims to demonstrate that the paternal gene SHORT SUSPENSOR (SSP) regulates YODA signaling through a parent‑of‑origin effect and to propose that SSP protein produced from paternal transcripts triggers zygotic YDA activity as a temporal cue for asymmetric division. Paternal SSP transcripts are delivered by sperm cells to the zygote and endosperm, where SSP protein transiently accumulates. Ectopic SSP protein expression activates YDA‑dependent signaling, confirming that paternal SSP regulates YODA activity and provides a temporal cue for the first asymmetric division.

Abstract

The YODA (YDA) mitogen-activated protein kinase pathway promotes elongation of the Arabidopsis zygote and development of its basal daughter cell into the extra-embryonic suspensor. Here, we show that the interleukin-1 receptor-associated kinase (IRAK)/Pelle-like kinase gene SHORT SUSPENSOR (SSP) regulates this pathway through a previously unknown parent-of-origin effect. SSP transcripts are produced in mature pollen but do not appear to be translated. Instead, they are delivered via the sperm cells to the zygote and the endosperm, where SSP protein transiently accumulates. Ectopic expression of SSP protein in the leaf epidermis is sufficient to activate YDA-dependent signaling. We propose that SSP protein produced from paternal transcripts upon fertilization triggers zygotic YDA activity, providing an essential temporal cue for the regulation of the asymmetric first division.