Abstract

Distant hybridization is widely used to develop crop cultivars, whereas the hybridization process of embryo abortion often severely reduces the sought-after breeding effect. The LEAFY COTYLEDON1 (LEC1) gene has been extensively investigated as a central regulator of seed development, but it is far less studied in crop hybridization breeding. Here we investigated the function and regulation mechanism of CmLEC1 from Chrysanthemum morifolium during its seed development in chrysanthemum hybridization. CmLEC1 encodes a nucleic protein and is specifically expressed in embryos. CmLEC1’s overexpression significantly promoted the seed-setting rate of the cross, while the rate was significantly decreased in the amiR-CmLEC1 transgenic chrysanthemum. The RNA-Seq analysis of the developing hybrid embryos revealed that regulatory genes involved in seed development, namely, CmLEA (late embryogenesis abundant protein), CmOLE (oleosin), CmSSP (seed storage protein), and CmEM (embryonic protein), were upregulated in the OE (overexpressing) lines but downregulated in the amiR lines vs. wild-type lines. Future analysis demonstrated that CmLEC1 directly activated CmLEA expression and interacted with CmC3H, and this CmLEC1–CmC3H interaction could enhance the transactivation ability of CmLEC1 for the expression of CmLEA. Further, CmLEC1 was able to induce several other key genes related to embryo development. Taken together, our results show that CmLEC1 plays a positive role in the hybrid embryo development of chrysanthemum plants, which might involve activating CmLEA’s expression and interacting with CmC3H. This may be a new pathway in the LEC1 regulatory network to promote seed development, one perhaps leading to a novel strategy to not only overcome embryo abortion during crop breeding but also increase the seed yield.

Highlights

  • Most plant species throughout the world rely on seed production for their reproduction, and seeds are of strategic significance to agriculture, the global food supply, and humanity[1]

  • Phylogenetic analysis confirmed that CmLEC1 is most closely related to AaLEC1 from Artemisia annua (Fig. 1b); the phylogenetic analysis of CmLEC1 with Arabidopsis NF-YB family revealed CmLEC1 to be clustered with Arabidopsis NF-YB6 and NF-YB9 (Fig. S1)

  • These results confirmed that the sequence isolated from chrysanthemum was a LEAFY COTYLEDON1 (LEC1) ortholog, designated here as CmLEC1

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Summary

Introduction

Most plant species throughout the world rely on seed production for their reproduction, and seeds are of strategic significance to agriculture, the global food supply, and humanity[1]. Embryo morphology and embryo maturation are important biological processes in the life cycle of plants. Normal seed development is critical for protecting genetic resources and sustaining crop yields. In this respect, normal embryo development is a key feature. Wild relatives of crop plants are vital reservoirs of genetic variability with respect to various economic characteristics, such as resistance against disease or insect pests, tolerance to abiotic stresses, an increased biomass, grain yield, and improved quality-related characteristics. Distant hybridization between plant varieties and wild resources is an effective way to improve the biotic and abiotic tolerance of crops and it creates many new genotypes. The ensuing hybrid offspring may be capable of greater environmental adaptability and can contribute to genetic diversity

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