Essential roles of autophagy in endosperm development in rice seed maturation

Essential roles of autophagy in metabolic regulation in endosperm development during rice seed maturation

Yuri Sera, Shigeru Hanamata, Shingo Sakamoto, Seijiro Ono, Kentaro Kaneko, Yuudai Mitsui, Tomoko Koyano, Naoko Fujita, Ai Sasou, Takehiro Masumura, Hikaru Saji, Ken-Ichi Nonomura, Nobutaka Mitsuda, Toshiaki Mitsui, Takamitsu Kurusu, Kazuyuki Kuchitsu

Scientific Reports 9, 18544 (2019) DOI:10.1038/s41598-019-54361-1


Autophagy, the recycling system of metabolites in eukaryotic cells, plays crucial roles in developmental processes, reproduction and biotic/abiotic-stress responses. However, the role in plants has been largely elusive.

We found that rice autophagy-deficient mutants set smaller seeds with chalky endosperms, in which starch granules were smaller and sparser than in the wild type (Figure). The activity of α-amylases, starch degradation enzymes, was abnormally activated in the mutant endosperm, and in contrast, the level of starch synthesis-promoting enzymes was reduced. The levels of heat shock-, oxidation- or high temperature-responsible proteins were elevated in the mutant endosperm. These results suggest the importance of autophagy in starch degradation and/or stress response pathways in rice endosperm development, and will be useful for breeding of high yielding varieties tolerant to environmental changes.

This work was achieved by collaboration of Tokyo University of Science, Suwa University of Science, Niigata University, National Institute of Advanced Industrial Science and Technology, National Institute of Genetics, Akita Prefectural University, Kyoto Prefectural University and National Institute for Environmental Studies, and was supported by NIG-JOINT (84A2018).


Figure: Mutant phenotypes in the endosperm of autophagy-deficient rice seeds
(A) The autophagy-deficient grain displays chalky appearance. (B) Scanning electron microscopic (top) and electron probe microscopic (bottom) images of endosperm sections. The starch granules had a lot of small pits in autophagy-deficient seeds (red arrows).

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