Genome analysis shows chloroplast acquisition without gene transfer in photosynthetic marine snails
Plants, algae, and some bacteria are capable of photosynthesis, in which solar energy is converted into sugar. Animals are generally unable to use this process to produce energy, but there are a few known exceptions. Some marine snails ingest chloroplasts from the algae, which they ingest into their cells. These chloroplasts retain their ability to photosynthesize within animal cells for several months and thus provide them with food obtained through photosynthesis. This procedure is called “kleptoplasty” and has attracted a lot of attention for over 50 years because of its amazing uniqueness in photosynthesis in animals.
An urgent question is how these sequestered chloroplasts retain their ability to photosynthesize without algae nuclei. Since the genome of the algae nucleus codes most of the proteins required for photosynthesis, chloroplasts isolated from algal cells immediately lose their ability to photosynthesize. Nevertheless, algae-eating sea snails retain this photosynthetic ability for months. There has been much debate about the mechanisms underlying the phenomenon that sequestered chloroplasts retain their photosynthetic abilities over the long term. A widely accepted hypothesis for kleptoplasty is the horizontal gene transfer of photosynthetic genes from algae to sea snails.
A team of researchers from the National Institute for Basic Biology (NIBB), together with employees from seven other Japanese institutions, has published the genome of the marine snail Plakobranchus ocellatus, type black eLife. “Since the sea snail is not a model organism, its genome analysis was very difficult compared to model organisms such as mice and fruit flies. In addition, good quality genetic information was not available for them. This situation consequently hampered the verification of the algae-derived horizontal gene transfer hypothesis, “said Shuji Shigenobu, a genome scientist and professor at NIBB, the corresponding author of the article is sea snail Animal core to be included based on newly revealed genomic data. “We looked very closely at the genome, but we found no evidence of photosynthetic genes encoded in the marine snail genome,” he said.
“We are facing a new challenge to answer the question: How does the marine snail retain this function without horizontal gene transfer?” Says Taro Maeda, the first and co-corresponding author of the paper. “Our genome data also provide information on this. We have found several candidate genes associated with long-term maintenance of photosynthetic activity. These genes, which are related to protein metabolism, tolerance to oxidative stress, and innate immunity, should then be highlighted in future studies. “
The mechanisms underlying kleptoplasty are still unclear. A further understanding of this phenomenon could lead us to innovative biotechnologies that could, for example, give other animal cells photosynthetic abilities in the future.
“Chloroplast acquisition without gene transfer in kleptoplastic sea snails, Plakobranchus ocellatus” by Taro Maeda, Shunichi Takahashi, Takao Yoshida, Shigeru Shimamura, Yoshihiro Takaki, Yukiko Nagai, Atsushi Toyoda, Yutaka Suzuki, Asuka Arimoto Mits, Nasiyashi, Noishu Ishi Maruyama, Jun Minagawa, Junichi Obokata, Shuji Shigenobu
DOI: https: /
Prof. Shuji Shigenobu
National Institute for Basic Biology
Dr. Taro Maeda