著者

Uji Toshiki Endo Harune Mizuta Hiroyuki

出版者

Frontiers Media

雑誌

Frontiers in plant science (ISSN:1664462X)

巻号頁・発行日

vol.11, pp.60, 2020-02

被引用文献数

20

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The transition from the vegetative to sexually reproductive phase is the most dynamic change to occur during a plant's life cycle. In the present study, we showed that the ethylene precursor 1-aminocylopropane-1-carboxylic acid (ACC) induces sexual reproduction in the marine red alga Pyropia yezoensis independently from ethylene. Exogenous application of ACC, which contains a three membered carbocyclic ring, promoted the formation of spermatia and carporspores in gametophytes, whereas ethephon, an ethylene-releasing compound, did not stimulate sexual reproduction. In addition, an ACC analog, 1-aminocyclobutane-1-carboxylic acid (ACBC), which contains a four membered carbocyclic ring, promoted sexual reproduction and enhanced tolerance to oxidative stress in the same manner as ACC, but 1-aminocyclopentane-1-carboxylic acid (cycloleucine; which contains a cyclopentane ring) did not. The application of ACC increased the generation of reactive oxygen species (ROS) and induced the expression of PyRboh gene encoding NADPH oxidase. ACC also stimulated the synthesis of ascorbate (AsA) by inducing transcripts of PyGalLDH, which encodes galactono-1,4-lactone dehydrogenase, the catalyst for the final enzymatic step of the AsA biosynthetic pathway. Conversely, ACC caused a decrease in the synthesis of glutathione (GSH) by repressing transcripts of PyGCL, which encodes glutamate cysteine ligase, the catalyst for the rate-limiting step in the formation of GSH. These results suggest a possible role played by ACC as a signaling molecule independent from ethylene in the regulation of sexual reproduction through alterations to the redox state in P. yezoensis.

著者

Mizuta Hiroyuki Uji Toshiki Yasui Hajime

出版者

Elsevier

雑誌

Algal research (ISSN:22119264)

巻号頁・発行日

vol.58, pp.102369, 2021-10

被引用文献数

5

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The process of biogenic silicon (Si) deposition in sporophytes of kelp (Saccharina japonica) was investigated by culturing sporophyte disks in the medium with and without hydrogen peroxide (H2O2). Culture with H2O2 remarkably promoted silicate-Si uptake by the disks. Silicate-Si uptake was completely inhibited by the treatment with potassium bromide (KBr), a competitive inhibitor of iodoperoxidase (IPO), even in the medium with H2O2. In addition, disk culture with phenol red in the medium with H2O2 resulted in the formation of bromophenol blue, indicating the presence of extracellular IPO. However, KBr treatment inhibited the formation of bromophenol blue in the medium with H2O2. These results showed that silicate-Si uptake is activated by extracellular IPO in the presence of radical oxygen species (ROS), such as H2O2. Interestingly, 1 mM salicylic acid also promoted silicate-Si uptake, even in the medium without H2O2. Furthermore, the allocation of silicate-Si to the soluble and cell wall-bound phlorotannin fractions using rhodamine 123 (R123), a tracer of biogenic Si, was estimated. Tracer fluorescence was detected in not only the soluble but also the cell wall-bound phlorotannin fraction. R123 fluorescence was histologically detected in the apoplasts of the epidermal and outer cortical layers of the disk, overlapping the histochemical distribution of IPO activity. These results suggested that silicate-Si uptake is activated by an oxidative burst induced by various stresses, and Si deposition is catalyzed by extracellular IPO in the presence of both ROS and phlorotannin in the extracellular matrix of sporophytes. Based on these findings, the hypothetical mechanisms of the extracellular silicate-Si uptake for defense responses in kelp were discussed.