Hosta capitata

Abstract: Cold temperatures are a major source of stress for plants and negatively impact crop yield. A possible way to protect plants is to treat them with antifreeze proteins (AFPs). Here, we investigated whether fish AFPs can shield the rare ornamental species Hosta capitata from low-temperature stress. We elucidated the expression patterns of the cold-inducible genes C-repeat binding factor 1 (CBF1) and dehydrin 1 (DHN1), as well as the antioxidant genes superoxide dismutase (SOD) and catalase (CAT). All were upregulated at low temperature (4 °C). With increasing exposure time, CBF1 and DHN1 expression generally rose (except CBF1 at 48 h). In contrast, SOD and CAT expression gradually declined from 6 to 48 h. Depending on exposure duration, AFP regulation of gene transcription varied with concentration. However, compared with other concentrations, 100 µg/L AFP reduced CBF1 and DHN1 expression and increased SOD and CAT expression in plants, regardless of exposure time. Both AFP I and III were likely to be most effective at protecting plants against cold stress at concentrations of 100 µg/L. Their involvement in H. capitata cold-stress treatment occurred through regulating the expression of important stress-response genes.

Abstract: The genus Hosta, which has a native distribution in temperate East Asia and a number of species ranging from 23 to 40, represents a taxonomically important and ornamentally popular plant. Despite its taxonomic and horticultural importance, the genus Hosta has remained taxonomically challenging owing to insufficient diagnostic features, continuous morphological variation, and the process of hybridization and introgression, making species circumscription and phylogenetic inference difficult. In this study, we sequenced 11 accessions of Hosta plastomes, including members of three geographically defined subgenera, Hosta, Bryocles, and Giboshi, determined the characteristics of plastomes, and inferred their phylogenetic relationships. We found highly conserved plastomes among the three subgenera, identified several mutation hotspots that can be used as barcodes, and revealed the patterns of codon usage bias and RNA editing sites. Five positively selected plastome genes (rbcL, rpoB, rpoC2, rpl16, and rpl20) were identified. Phylogenetic analysis suggested (1) the earliest divergence of subg. Hosta, (2) non-monophyly of subg. Bryocles and its two sections (Lamellatae and Stoloniferae), (3) a sister relationship between H. sieboldiana (subg. Giboshi) and H. ventricosa (subg. Bryocles), and (4) reciprocally monophyletic and divergent lineages of H. capitata in Korea and Japan, requiring further studies of their taxonomic distinction.