Loss of starch synthase IIa alleviates the negative impact of high temperature on rice starch during grain filling
- 1Akita Prefectural University
Abstract
High temperatures during grain filling stage are becoming increasingly frequent, compromising both grain and eating quality and thereby driving demand for heat-resilient cultivars. Such conditions are known to reduce the expression of granule-bound starch synthase I (GBSSI) and starch branching enzyme IIb (BEIIb), which are involved in starch biosynthesis, resulting in a decrease in amylose content and an increase in long-chain amylopectin. Thus, the present study introduced functional mutation in starch synthase IIa (SSIIa) that increases the proportion of short amylopectin chains to genetically compensate for the high-temperature-induced increase in amylopectin long chain. Rice lines carrying the ss2a mutation were grown at two locations with cooler (Akita) and warmer (Okayama) temperatures. Their grain traits, starch structure, and eating quality were compared. The ss2a mutant lines showed an increased proportion of short amylopectin chains as well as an increased apparent amylose content. Furthermore, these alterations in starch structure varied with the grain-filling temperature of the cultivation sites, ultimately affected eating quality. These results suggest that enriching short amylopectin chain via the ss2a mutation can counteract the increase in long amylopectin chain caused by high temperatures during grain filling, thereby maintaining a desirable starch structure and eating quality.
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BibTeX
@misc{hashimoto2026loss,
title = {{Loss of starch synthase IIa alleviates the negative impact of high temperature on rice starch during grain filling}},
author = {S. Hashimoto and R. Matsushima and N. F. Oitome and Y. Hosaka and S. Miura and N. Crofts and T. Yamamoto and N. Fujita},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.28.754565},
url = {https://www.biorxiv.org/content/10.64898/2026.09.28.754565v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Loss of starch synthase IIa alleviates the negative impact of high temperature on rice starch during grain filling
AU - S. Hashimoto
AU - R. Matsushima
AU - N. F. Oitome
AU - Y. Hosaka
AU - S. Miura
AU - N. Crofts
AU - T. Yamamoto
AU - N. Fujita
PY - 2026
DA - 2026/09/28
PB - bioRxiv
DO - 10.64898/2026.09.28.754565
UR - https://www.biorxiv.org/content/10.64898/2026.09.28.754565v1
AB - High temperatures during grain filling stage are becoming increasingly frequent, compromising both grain and eating quality and thereby driving demand for heat-resilient cultivars. Such conditions are known to reduce the expression of granule-bound starch synthase I (GBSSI) and starch branching enzyme IIb (BEIIb), which are involved in starch biosynthesis, resulting in a decrease in amylose content and an increase in long-chain amylopectin. Thus, the present study introduced functional mutation in starch synthase IIa (SSIIa) that increases the proportion of short amylopectin chains to genetically compensate for the high-temperature-induced increase in amylopectin long chain. Rice lines carrying the ss2a mutation were grown at two locations with cooler (Akita) and warmer (Okayama) temperatures. Their grain traits, starch structure, and eating quality were compared. The ss2a mutant lines showed an increased proportion of short amylopectin chains as well as an increased apparent amylose content. Furthermore, these alterations in starch structure varied with the grain-filling temperature of the cultivation sites, ultimately affected eating quality. These results suggest that enriching short amylopectin chain via the ss2a mutation can counteract the increase in long amylopectin chain caused by high temperatures during grain filling, thereby maintaining a desirable starch structure and eating quality.
ER -