Abstract
The interaction of C-TERMINALLY ENCODED PEPTIDES (CEPs) with CEP RECEPTOR1 (CEPR1) controls root growth and development, as well as nitrate uptake, but has no known role in determining yield. We used physiological, microscopic, molecular, and grafting approaches to demonstrate a reproductive tissue-specific role for CEPR1 in controlling yield and seed size. Independent Arabidopsis (Arabidopsis thaliana) cepr1 null mutants showed disproportionately large reductions in yield and seed size relative to their decreased vegetative growth. These yield defects correlated with compromised reproductive development predominantly in female tissues, as well as chlorosis, and the accumulation of anthocyanins in cepr1 reproductive tissues. The thinning of competing reproductive organs to improve source-to-sink ratios in cepr1, along with reciprocal bolt-grafting experiments, demonstrated that CEPR1 acts locally in the reproductive bolt to control yield and seed size. CEPR1 is expressed throughout the vasculature of reproductive organs, including in the chalazal seed coat, but not in other seed tissues. This expression pattern implies that CEPR1 controls yield and seed size from the maternal tissue. The complementation of cepr1 mutants with transgenic CEPR1 rescued the yield and other phenotypes. Transcriptional analyses of cepr1 bolts showed alterations in the expression levels of several genes of the CEP-CEPR1 and nitrogen homeostasis pathways. This transcriptional profile was consistent with cepr1 bolts being nitrogen deficient and with a reproductive tissue-specific function for CEP-CEPR1 signaling. The results reveal a local role for CEPR1 in the maternal reproductive tissue in determining seed size and yield, likely via the control of nitrogen delivery to the reproductive sinks.
Highlights
Leucine-rich repeat receptor-like kinases (LRR-RLK) are one of the largest gene families in plants, comprising more than 220 members in Arabidopsis (Arabidopsis thaliana) (Gou et al., 2010)
Since vegetative leaves mobilise resources to the bolt and other reproductive tissues, we examined whether loss of C-terminally Encoded Peptide (CEP) RECEPTOR 1 (CEPR1) function affected yield
The limited seeds produced by the cepr1 mutants were smaller and more diverse in size compared to wild-type (WT) seeds (Fig. 1, J and K)
Summary
Leucine-rich repeat receptor-like kinases (LRR-RLK) are one of the largest gene families in plants, comprising more than 220 members in Arabidopsis (Arabidopsis thaliana) (Gou et al., 2010). ENCODED PEPTIDE RECEPTOR 1 (CEPR1) in Arabidopsis, and its functional orthologue. Terminally Encoded Peptide (CEP) family (Tabata et al, 2014). CEP genes, each encoding one or more conserved 15-amino acid CEP domains from which the secreted, mature CEP peptide hormones are derived (Ogilvie et al, 2014). Since the identification of CEPR1 as a CEP receptor (Tabata et al, 2014), its developmental and physiological role has been defined primarily in the context of roots.
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