We conducted a morphological observation and molecular phylogenetic analyses on bladed Bangiales collected from natural populations on Shikinejima Island and Hachijojima Island of the Izu Islands, southern central Japan. The morphological features of the gametophytic blades such as the blade shape, blade margin and reproductive cell divisions were extremely similar to those parameters of Neoporphyra haitanensis, a species cultivated in southern China, and Neoporphyra dentata. However, the blades collected from the two islands were thicker than the blades of N. dentata; this feature was the same as that of N. haitanensis. The chloroplast RUBISCO spacer sequences of present samples were identical to the sequences of N. haitanensis from China. Moreover, phylogenetic positions of three conchocelis strains isolated from the blades on the two islands were examined based on concatenated sequences of the chloroplast rbcL gene and nuclear 18S rRNA. The results showed that the strains were resolved in a clade including N. haitanensis; however, the strains were separated from N. haitanensis in China. Therefore, the bladed Bangiales from the two islands were identified as N. haitanensis. The present study is the first record of N. haitanensis in natural populations in Japan.

Many abiotic stresses induce the generation of nitric oxide (NO) in plant tissues, where it functions as a signal molecule in stress responses. Plants modulate NO by oxidizing it to NO 3 − with plant hemoglobin (GLB), because excess NO is toxic to cells. At least eight genes encoding GLB have been identified in soybean, in three clades: GLB1, GLB2, and GLB3. However, it is still unclear which GLB genes are responsible for NO regulation under abiotic stress in soybean. We exposed soybean roots to flooding, salt, and two NO donors-sodium pentacyanonitrosylferrate (III) dihydrate (SNP) and S-nitroso-N-acetyl-d,l-penicillamine (SNAP)-and analyzed expression of GLB genes. GmGLB1, one of two GLB1 genes of soybean, significantly responded to both SNP and SNAP, and its induction was almost completely repressed by a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. GmGLB1 responded to flooding but not to salt, suggesting that it is responsible for NO regulation under NO-inducing abiotic stresses such as flooding. GmGLB3, one of two GLB3 genes of soybean, did not respond to NO donors at all but did respond to flooding, at a lower level than GmGLB1. These results suggest that flooding induces not only NO but also unknown factor(s) that induce GmGLB3 gene in soybean.

SUMMARYThe Izu Islands of southcentral Japan are thought to fall within the distribution range of Neoporphyra dentata. However, the gametophytic blades of Bangiales collected from Shikinejima and Hachijojima, Izu Islands, were identified as Neoporphyra haitanensis in our previous study. Thus, it became uncertain whether N. dentata is distributed in the Izu Islands, including Shikinejima. To clarify whether N. dentata grows on Shikinejima, we conducted a further distribution survey of N. dentata on the island. The morphological features of the blade samples collected from an additional sampling site on Shikinejima were more similar to those of N. dentata than to those of N. haitanensis: the blade thickness and the division formula of spermatangia resembled those of the former species rather than the latter species. However, the division formula of zygotosporangia was different from those of either species. The phylogenetic analyses of the rbcL gene indicated that the samples were resolved in a clade including N. dentata collected from Shirahama, Chiba Prefecture, and Enoshima, Kanagawa Prefecture, Honshu, Japan. The p‐distances of the chloroplast rbcL gene and nuclear 18S rRNA also supported identification of the samples as N. dentata. The results demonstrated that N. dentata is also distributed on Shikinejima with co‐occurring N. haitanensis, and that the island materials of the two species are genetically different from other materials of the two species, respectively.