Single-cell RNA-seq reveals a link of ovule abortion and sugar transport in Camellia oleifera

Abstract

Camellia oleifera is the most important woody oil crop in China. Seed number per fruit is an important yield trait in C. oleifera. Ovule abortion is generally observed in C. oleifera and significantly decreases the seed number per fruit. However, the mechanisms of ovule abortion remain poorly understood at present. Single-cell RNA sequencing (scRNA-seq) was performed using mature ovaries of two C. oleifera varieties with different ovule abortion rates (OARs). In total, 20,526 high-quality cells were obtained, and 18 putative cell clusters were identified. Six cell types including female gametophyte, protoxylem, protophloem, procambium, epidermis, and parenchyma cells were identified from three main tissue types of ovule, placenta, and pericarp inner layer. A comparative analysis on scRNA-seq data between high- and low-OAR varieties demonstrated that the overall expression of CoSWEET and CoCWINV in procambium cells, and CoSTP in the integument was significantly upregulated in the low-OAR variety. Both the infertile ovule before pollination and the abortion ovule producing after compatible pollination might be attributed to selective abortion caused by low sugar levels in the apoplast around procambium cells and a low capability of hexose uptake in the integument. Here, the first single-cell transcriptional landscape is reported in woody crop ovaries. Our investigation demonstrates that ovule abortion may be related to sugar transport in placenta and ovules and sheds light on further deciphering the mechanism of regulating sugar transport and the improvement of seed yield in C. oleifera.

Advances in Single-Cell Transcriptome Sequencing and Spatial Transcriptome Sequencing in Plants

“…Meanwhile, the authors also proposed that ovule abortion may be related to sugar transport in the placenta and ovule. This study reports for the first time a single-cell transcriptional landscape in the ovary of a woody crop, providing new insight for further deciphering the mechanisms of sugar transport regulation and seed yield enhancement in C. oleifera [ 48 ]. Using scRNA-seq technology, 14,535 cells were identified from the outer ovule of Gossypium hirsutum at different stages of development, three main cell types were identified (fiber, non-fiber epidermis, and outer pigment layer), and the development trajectory of the outer ovule fiber cells was reconstructed.…”

“…ScRNA-seq developmental trajectories and regulatory networks [40] Manihot esculenta leaf developmental trajectories and photosynthesis [41] Camellia sinensis leaf gene expression network [42] Hevea brasiliensis leaf cell-specific gene expression patterns [43] Taxus wallichiana var. chinensis leaf gene regulatory network [44] Fragaria × ananassa leaf aingle-cell mapping after infection [45] Nicotiana tabacum corolla single-cell metabolic heterogeneity [46] Bombax ceiba capsule cell developmental trajectories and regulatory networks [47] Camellia oleifera ovule gene regulatory network [48] Gossypium ovule gene regulatory network [49,50] Solanum lycopersicum stem SnRNA-seq spatial and temporal development trajectory [51] Arabidopsis thaliana seed construction of cell map [52] Mesembryanthemum crystallinum leaf gene expression pattern [53] Arabidopsis thaliana leaf Spatial transcriptome sequencing spatial expression patterns of genes [54] inflorescence spatial development characteristics [55,56] Populus tremula leafbud spatial development characteristics [55,56] Picea abies female cone spatial development characteristics [55][56][57] Solanum lycopersicum fruit spatial development trajectory [58] callus gene regulatory network [59] Brassica rapa var. glabra leaf gene regulatory network/heat stress [60]/ [61] Portulaca oleracea leaf spatial gene expression patterns [62] Phalaenopsis aphrodite flower spatial and temporal trajectory of development [63] Populus stem gene regulatory network [64] Arabidopsis thaliana leaf ScRNA-seq + single -cell transcriptome spatial development trajectory [65] Populus stem gene regulatory network [66] 2.2.1.…”

“…fruit/seed chalazal cyst AT2G44240, AT4G13380 [26] chalazal nodule AT5G10440, AT1G44090 [26] initiated fiber cell cluster HD1, BZR1, MYB2, TRY, HOX1 [47] epidermal cell HIC, CoAKR, CoCYP81E8, CoUGT73C5, CoUGT91A1 [47,48] synergid cell CoECA1 [48] procambium cell CoDOF4.6 [48] fibre cell MYB25-like, MYB25, MML9, HOX3, XTH [49,50] ovule ToFZY2, ToFZY3, Solyc03g112460, PIN5, ARF7, ARF9, IAA14, IAA35 [58] ovary wall ToFZY1, ToFZY5 [58] ovary wall/pericarp ToFZY5, PIN6, PIN7, PIN1, LAX3, ARF9, IAA17…”