A point mutation in LTT1 enhances cold tolerance at the booting stage in rice

Abstract

The cold tolerance of rice at the booting stage is a main factor determining sustainability and regional adaptability. However, relatively few cold tolerance genes have been identified that can be effectively used in breeding programmes. Here, we show that a point mutation in the low‐temperature tolerance 1 (LTT1) gene improves cold tolerance by maintaining tapetum degradation and pollen development, by activation of systems that metabolize reactive oxygen species (ROS). Cold‐induced ROS accumulation is therefore prevented in the anthers of the ltt1 mutants allowing correct development. In contrast, exposure to cold stress dramatically increases ROS accumulation in the wild type anthers, together with the expression of genes encoding proteins associated with programmed cell death and with the accelerated degradation of the tapetum that ultimately leads to pollen abortion. These results demonstrate that appropriate ROS management is critical for the cold tolerance of rice at the booting stage. Hence, the ltt1 mutation can significantly improve the seed setting ability of cold‐sensitive rice varieties under low‐temperature stress conditions, with little yield penalty under optimal temperature conditions. This study highlights the importance of a valuable genetic resource that may be applied in rice breeding programmes to enhance cold tolerance.

Genome-Wide Association Analysis for Salt–Induced Phenotypic and Physiologic Responses in Rice at Seedling and Reproductive Stages

“…In order to eliminate the effects of different developing processes on ST-phenotyping, we treated each accession with salt stress at a uniform time, that is, the date of the pulvinus of flag leaf and penultimate leaf reached together. This time point is often defined as rice entering reproductive stage and is easily determined by eye observation ( Hoshikawa, 1989 ; Xu et al, 2020 ). This design allowed us to establish a uniform standard to test rice ST tolerance at reproductive stage in greenhouse, and to ultimately obtain ST phenotypes as precise as possible for the subsequent analysis.…”

“…Distilled water was added every day to keep the whole volume. In rice, booting stage could be approximately judged as the pulvinus of flag leaf and penultimate leaf were overlapped ( Hoshikawa, 1989 ; Xu et al, 2020 ). And so, the date that the pulvinus of flag leaf and penultimate leaf reached together was used to start salt treatment for each accession.…”

Functions of Redox Signaling in Pollen Development and Stress Response

“…Cold stress causes ROS accumulation, which leads to tapetum degradation and pollen abortion. A point mutation of the Low Temperature Tolerance 1 ( LTT1 ) gene prevents ROS overproduction, allowing for correct pollen development, thereby improving the cold tolerance and seed setting ability of rice [ 96 ].…”

Cold‐adaptive evolution at the reproductive stage in Geng/japonica subspecies reveals the role of OsMAPK3 and OsLEA9

“…Low temperatures not only affect the growth and development of rice plants, but are also one of the main environmental factors limiting rice production and geographic distribution (Sperotto et al., 2018). Cold stress at the vegetative stage (germination and seedlings) often results in the lower survival rate of seedlings, slower seedling growth, and fewer tillers, while cold stress at the reproductive stage (booting and flowering) affects microspore development and pollen fertility, which directly influence rice yield and quality (Xu et al., 2020). In the context of more frequent extreme weather events around the world, cold stress at the reproductive stage also occurs more frequently in high‐latitude and high‐altitude regions.…”