# Rice sucrose transporter 1, OsSUT1, confers to alleviation of the high temperature stress in rice grain filling

## TL;DR

The OsSUT1 gene in rice helps reduce damage from high temperatures during grain filling, improving seed quality.

## Contribution

OsSUT1 is identified as a key gene that alleviates high-temperature stress during rice grain filling.

## Key findings

- The OsSUT1 gene is located in a region on chromosome 3 that reduces high-temperature injury in rice.
- Kasalath OsSUT1 has higher expression and reduces high-temperature damage compared to Nipponbare OsSUT1.
- Transformants with Kasalath OsSUT1 show significant alleviation of high-temperature injury during grain filling.

## Abstract

Quantitative trait loci involved in reducing high temperature injury during grain filling were investigated using fifty-four lines of the chromosome segment substitution lines (CSSLs) of the indica cultivar Kasalath in the japonica cultivar Nipponbare background. The ratio of chalky seeds was examined when they were ripened under the high-temperature conditions. Among these lines, SL13 seeds showed an obvious trait of alleviating injury. In SL13, a part of the chromosome 3 was substituted with the Kasalath genome, which contained a locus of this trait locus. Fine mapping of this locus using the progenies obtained by crossing SL13 with Nipponbare narrowed it down to a region of 3.36–3.81 Mb on chromosome 3. This region included the OsSUT1 gene encoding sucrose transporter 1. The Nipponbare OsSUT1 contained 19-nucleotide insertion in the promoter region, suggesting that this diversity might affect the transcription level of this gene. The progeny plants of SL13 containing the Kasalath OsSUT1, which had a significantly higher expression level of this gene, obviously reduced the high-temperature injury. Transformants carrying the Kasalath OsSUT1 gene showed significant alleviation in the high-temperature injury during grain filling. Our results indicate that OsSUT1 is a major factor consisting of the locus involved in reducing the high temperature injury in SL13. These results suggest that the enhanced function of OsSUT1 provides sufficient carbon assimilates to immature seeds even under high temperature conditions, leading to normal seed formation.