Early selection of bZIP73 facilitated adaptation of japonica rice to cold climates

Abstract

Cold stress is a major factor limiting production and geographic distribution of rice (Oryza sativa). Although the growth range of japonica subspecies has expanded northward compared to modern wild rice (O. rufipogon), the molecular basis of the adaptation remains unclear. Here we report bZIP73, a bZIP transcription factor-coding gene with only one functional polymorphism (+511 G>A) between the two subspecies japonica and indica, may have facilitated japonica adaptation to cold climates. We show the japonica version of bZIP73 (bZIP73Jap) interacts with bZIP71 and modulates ABA levels and ROS homeostasis. Evolutionary and population genetic analyses suggest bZIP73 has undergone balancing selection; the bZIP73Jap allele has firstly selected from standing variations in wild rice and likely facilitated cold climate adaptation during initial japonica domestication, while the indica allele bZIP73Ind was subsequently selected for reasons that remain unclear. Our findings reveal early selection of bZIP73Jap may have facilitated climate adaptation of primitive rice germplasms.

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

“…We found that the expression level of AOX1a and AOX1b in ltt1 was more than 20 times higher than that in WT (Figure 4c). Because the activities of SODs and peroxidases appear to correlate positively with cold tolerance in rice (Kim, Choi, Cho, & Kim, ; Lee, Kwon, & Kim, ; Liu et al, ), we further detected the activity of the related enzymes in ltt1 and WT. The results showed that the activities of these enzymes in the mutant plants increased significantly (Figure 4d,e), which may help the mutant to eliminate the excessive ROS more effectively.…”

“…Although natural variation in CTB4a appears to enhance the tolerance of rice to cold stress (Zhang et al, ), some of the varieties with the most effective haplotype (Hap1), such as DAOHUAXIANG and DONGNONG428, are highly sensitive to cold stress during the booting stage. Similarly, bZIP73 was identified as a QTL for seedling chilling tolerance (Liu et al, ), and the function of this gene on cold tolerance at the booting stage could only be observed in transgenic lines (Liu et al, ). In view of the severe damage of booting stage cold stress on rice yield and the functional uncertainties of the currently reported cold tolerance genes, there is an urgent need to provide effective cold tolerant genetic resources for traditional breeding.…”

“…On the other hand, increased ROS level would trigger multiple regulatory networks such as MAPK cascades and MYB‐ and WRKY‐mediated transcriptional regulation to activate cold‐responsive signalling pathways (Cheng et al, ; Peres, Basu, Ramegowda, Braga, & Pereira, ; Tao et al, ; Xie, Kato, & Imai, ; Zhang et al, ; Zhang et al, ). When plants continue to suffer from severe cold stress, the intracellular ROS would accumulate excessively, leading to a series of cytotoxic effects such as cell death, lipid peroxidation, photosynthetic rate reduction, growth retardation, and even seedling death or spikelet sterility (Liu et al, ; Sato, Masuta, Saito, Murayama, & Ozawa, ; Suzuki et al, ; Tovuu et al, ). Generally, over accumulation of ROS in the anther during microspore development would cause premature tapetal PCD (Luo et al, ; Zheng et al, ), whereas reduced ROS content would delay the PCD process in the tapetum (Yi et al, ).…”

Coordination of light, circadian clock with temperature: The potential mechanisms regulating chilling tolerance in rice

“…Usually, determination of chilling tolerance in rice at seedling stage uses the survival rates of rice seedlings after chilling treatment as the primary indicator (Ma et al 2015; Lv et al 2017; Zhang et al 2017b; Liu et al 2018a; Mao et al 2019). Identification of chilling tolerance at booting stage is typically determined based on yield traits such as seed setting rates and relative seed setting rates, together with pollen fertility (Zhang et al 2017b; Liu et al 2019).…”

Cold tolerance in rice plants is partially controlled by root responses

“…Given its tropical origin, cultivated rice germplasm genetic variability is very limited to identify cold stress tolerance genes and alleles (Byun et al 2017). A few examples of alleles associated with low temperature tolerance are derived from japonica subspecies, as COLD1 jap and bZIP73 jap (Ma et al 2015; Liu et al 2018). Indeed, transferring the japonica alleles to indica rice genotypes increased its cold tolerance.…”