Implications of the gene for F1–ATPase β subunit (<i>AtpB</i>) for the grain quality of rice matured in a high-temperature environment

Abstract

Rice grain filling is impaired by high-temperature stress during seed development. This event results in reduced grain yield and quality because of formation of smaller and chalky grains, and often causes problems in agriculture. Hightemperature stress causes disorders in primary metabolism pathways including ATP accumulation in the developing seeds. To determine the effect on the genes for ATP biosynthesis, we created the transformant rice plants in which expression of an F1-ATPase β subunit gene (AtpB) was reduced by its RNAi gene, and elevated in developing seeds by its overexpression using the GlutelinB4 promoter. The transformants, which showed a high level of ATP accumulation as well as abundant AtpB transcript in the developing seeds, showed acquired tolerance to high-temperature stress during seed development because the ratio of perfect grains without any chalky part was significantly increased. In contrast, transformants harboring the RNAi gene showed reduction of grain quality with increase of ratio of white-core and white-berry grains when they were developed in the normal growth condition. Most of these seeds never germinated, and the RNAi transgene was poorly inherited by the progenies. These results suggest that AtpB plays important roles in rice seed development and that its gene expression is strongly influenced by high-temperature stress during the grain filling stage.

Overexpression of rice OsLEA5 relieves the deterioration in seed quality caused by high-temperature stress

“…High-temperature stress induces downregulation of the expression of several genes involved in starch biosynthesis, as well as those involved in sucrose import and degradation, resulting in insufficient ATP production in the sink organs (Yamakawa and Hakata 2010;Yamakawa et al 2007). We have shown that tolerance to high-temperature stress is acquired by overexpression of the gene for F1-ATPase β subunit (AtpB) in rice transformants, as evidenced by a significant increase in the ratio of perfect grains without any chalky part (Kusano et al 2016).…”

“…(A) Amount of the OsLEA5 transcript in the transformants. Total RNA was prepared from developing seeds (15 DAF) as described previously (Kusano et al 2016), and subjected to real time RT-PCR analysis using the Thunderbird kit (Toyobo, Osaka, Japan). Numbers with prefix # indicate the individual RNAi transformants.…”

“…no. AK061818) was amplified by PCR, and inserted in pCAMBIA1300 (https://www.addgene.org/vector-database/5930/) in the sense direction that was driven by the GluB4 promoter(Qu and Takaiwa 2004;Kusano et al 2016). PCR primers were listed in Supplementary TableS1.…”