Live and let die: a REM complex promotes fertilization through synergid cell death in Arabidopsis

Abstract

Fertilization in flowering plants requires a complex series of coordinated events involving interaction between the male and female gametophyte. We report here molecular data on one of the key events underpinning this process -the death of the receptive synergid cell and the coincident bursting of the pollen tube inside the ovule to release the sperm. We show that two REM transcription factors, VALKYRIE (VAL) and VERDANDI (VDD), both targets of the ovule identity MADS-box complex SEEDSTICK-SEPALLATA3, interact to control the death of the receptive synergid cell. In vdd-1/+ mutants and VAL_RNAi lines, we find that GAMETOPHYTIC FACTOR 2 (GFA2), which is required for synergid degeneration, is downregulated, whereas expression of FERONIA (FER) and MYB98, which are necessary for pollen tube attraction and perception, remain unaffected. We also demonstrate that the vdd-1/+ phenotype can be rescued by expressing VDD or GFA2 in the synergid cells. Taken together, our findings reveal that the death of the receptive synergid cell is essential for maintenance of the following generations, and that a complex comprising VDD and VAL regulates this event.

The Molecular Dialog between Flowering Plant Reproductive Partners Defined by SNP-Informed RNA-Sequencing

“…consequence of highly coordinated cell-cell signaling requiring pollen tube and synergid transcriptional networks (Leydon et al, 2013;Liang et al, 2013;Mendes et al, 2016), expression of cell surface signaling molecules (Escobar-Restrepo et al, 2007;Kessler et al, 2010;Lindner et al, 2015;Liu et al, 2016), and Ca 2+ fluxes that define which of two synergids receives the pollen tube (Denninger et al, 2014;Ngo et al, 2014). Using SNP-informed RNA-seq analysis of myb triple mutant compared with wild-type pollinations, we have provided a comprehensive set of genes expressed by pollen tubes that mediate interactions with female cells required for pollen tube burst, sperm release and synergid degeneration.…”

Arabinogalactan Proteins as Interactors along the Crosstalk between the Pollen Tube and the Female Tissues

“…VDD may act downstream of these cell surface signaling components (Matias-Hernandez et al, 2010). Recently, VDD and VALKYRIE (VAL), also a member of the REM family, were shown to act as a complex regulating the death of the receptive synergid cell, and the death (by bursting) of the pollen tube after growth arrest (Mendes et al, 2016). …”

A blueprint of seed desiccation sensitivity in the genome ofCastanospermum australe

“…Among these were the transcription factors (TFs) VERDANDI and MYB44 - like . VERDANDI participates in ovule identity complex and, when mutated, affects embryo sac differentiation in A. thaliana (Matias-Hernandez et al , 2010; Mendes et al , 2016). Interestingly, VERDANDI and MYB44 - like were also retained in intermediate-seeded species.…”

“…Illumina reads were error-corrected using Lighter (Song et al , 2014) and assembled using SparseAssembler (Ye et al , 2012). A hybrid assembly was produced with DBG2OLC (Ye et al , 2016) and the contigs were reordered and connected into scaffolds using SSPACE-LongRead (Boetzer & Pirovano, 2014). The assembly was polished using Sparc (Ye et al , 2012) and Pilon (Walker et al , 2014).…”