A conserved role for CUP‐SHAPED COTYLEDON genes during ovule development

Abstract

SUMMARYThe evolution of plant reproductive strategies has led to a remarkable diversity of structures, especially within the flower, a structure characteristic of the angiosperms. In flowering plants, sexual reproduction depends notably on the development of the gynoecium that produces and protects the ovules. In Arabidopsis thaliana, ovule initiation is promoted by the concerted action of auxin with CUC1 (CUP-SHAPED COTY-LEDON1) and CUC2, two genes that encode transcription factors of the NAC family (NAM/ATAF1,2/CUC). Here we highlight an additional role for CUC2 and CUC3 in Arabidopsis thaliana ovule separation. While CUC1 and CUC2 are broadly expressed in the medial tissue of the gynoecium, CUC2 and CUC3 are expressed in the placental tissue between developing ovules. Consistent with the partial overlap between CUC1, CUC2 and CUC3 expression patterns, we show that CUC proteins can physically interact, both in yeast cells and in planta. We found that the cuc2;cuc3 double mutant specifically harbours defects in ovule separation, producing fused seeds that share the seed coat, and suggesting that CUC2 and CUC3 promote ovule separation in a partially redundant manner. Functional analyses show that CUC transcription factors are also involved in ovule development in Cardamine hirsuta. Additionally we show a conserved expression pattern of CUC orthologues between ovule primordia in other phylogenetically distant species with different gynoecium architectures. Taken together these results suggest an ancient role for CUC transcription factors in ovule separation, and shed light on the conservation of mechanisms involved in the development of innovative structures.

Three Rice NAC Transcription Factors Heteromerize and Are Associated with Seed Size

“…Also, these subtle variations indicate toward a degree of distinctness along with redundancy in the roles of the three seed specific NAC genes during rice seed development. In a similar manner, CUC genes involved in the initiation of ovule formation and cotyledon separation in Arabidopsis , show partially overlapping expression pattern and also interact amongst themselves (Goncalves et al, 2015). Since the NAC genes analyzed here also interact, as is shown further in the paper, the differences in their levels in the five accessions with variable seed weights, may modulate downstream seed development processes to variable extents.…”

Depletion of Key Meiotic Genes and Transcriptome-Wide Abiotic Stress Reprogramming Mark Early Preparatory Events Ahead of Apomeiotic Transition

“…Although the micro-dissected RNA-seq did not give consistent presence calls for several NACs in laser-captured single cell transcriptomes presumably due to experimental noise, NAC032, NAC002 and NAC103 homologs of Boechera were consistently present in Apo-1 apomeiotic cell types such as the MMC and surrounding ovular cells (Schmidt et al, 2014) (Supplementary Table S4). A recent work identified novel role of NAC family members in ovule separation (Goncalves et al, 2015), thus in addition to stress regulation, NACs might govern early reproductive development. A number of NACs are also known for their non-cell-autonomous movement via movement of their mobile mRNA (Thieme et al, 2015); therefore, one possibility may be that they maternally control decisions on sexual or apomictic reproductive development.…”

Multiscale quantification of morphodynamics: MorphoLeaf, software for 2-D shape analysis

“…The cuc2-1 mutant and CUC2-CUC2-VENUS reporter line have been described elsewhere Gonçalves et al, 2015). The mir164a-4 mutant (Nikovics et al, 2006) that shows a higher level of leaf complexity was used to validate the hierarchy procedure.…”