出口 亜由美

KEY MESSAGE: Epidendrum produces 2n gametes with high frequency. This paper is the first to report on multiple pathways for forming 2n gametes, meiotic defeats, and pre-meiotic chromosome doubling. Unreduced 2n reproductive cells are predominantly involved in pathways that lead to polyploid plants. Although one of the most common pathways for inducing 2n gametes is through meiotic defects, a small set of isolated species alternatively generates 2n gametes from tetraploid pollen mother cells in the pre-meiotic phase. Hence, determining the mechanisms underlying 2n gamete formation is critical to improving breeding programmes and understanding plant evolution. We investigated sporads to reveal the pathway(s) accounting for the formation and frequencies of 2n gametes in wild species and interspecific hybrids in the genus Epidendrum. We investigated different types of sporads with varying frequencies, sizes, and viability in the wild species and hybrids of the genus Epidendrum. Large tetrad-estimated pre-meiotic chromosome doubling was observed in wild species. The Epidendrum is unique in that it forms 2n pollens via two pathways, namely, meiotic defects and pre-meiotic chromosome doubling. These two pathways of 2n pollen formation could influence the high diversity generation of polyploidy with different degrees of heterozygosity and genetic backgrounds in the genus Epidendrum. Therefore, these findings are proposed to influence polyploid breeding of Epidendrum via 2n pollen, helping us understand evolution and speciation via unreduced 2n gamete formation in Orchidaceae.

When used in closed-type plant factories, light-emitting diode (LED) illumination systems have the particular advantages of low heat emission and high luminous efficiency. The effects of illumination quality and intensity on the growth and morphogenesis of many plant species have been examined, but improvements are needed to optimize the illumination systems for better plant products with lower resource investments. In particular, new strategies are needed to reduce the wastage of plant products related to leaf senescence, and to better control the ingredients and appearance of leafy vegetables. Although the quality of light is often altered to change the characteristics of plant products, the transcriptional status underlying the physiological responses of plants to light has not been established. Herein, we performed a comprehensive gene expression analysis using RNA-sequencing to determine how red, blue, and red/blue LEDs and fluorescent light sources affect transcriptome involved in the leaf aging of leaf lettuce. The RNA-sequencing profiling revealed clear differences in the transcriptome between young and old leaves. Red LED light caused large variation between the two age classes, while a pure or mixed blue LED light spectrum induced fewer transcriptome differences between young and old leaves. Collectively, the expression levels of genes that showed homology with those of other model organisms provide a detailed physiological overview, incorporating such characteristics as the senescence, nutrient deficiency, and anthocyanin synthesis of the leaf lettuce plants. Our findings suggest that transcriptome profiles of leaf lettuce grown under different light sources provide helpful information to achieve better growth conditions for marketable and efficient green-vegetable production, with improved wastage control and efficient nutrient inputs.