Molecular Plant Breeding 2024, Vol.15, No.6, 429-441 http://genbreedpublisher.com/index.php/mpb 430 This review systematically investigates the regulatory mechanisms of temperature, light, and water (humidity) on MS gene expression in rice, including identifying key genetic factors and understanding their interaction with environmental factors that control MS. This review highlights the molecular and genetic basis of MS regulation, with a focus on PGMS, TGMS, and HGMS lines, and to reveal new insights into the environmental regulation of MS genes by integrating data from various genomic, transcriptomic, and molecular analyses. This review aims to develop new strategies for breeding disaster-resistant rice varieties that can adapt to changing environmental conditions, thereby ensuring food security and sustainable agricultural practices. 2 Temperature Regulation of MS Genes 2.1 TGMS in rice TGMS in rice is a crucial mechanism that facilitates the development of hybrid rice varieties (Hussain et al., 2012). TGMS lines exhibit MS under specific temperature conditions, which can be reversed when the temperature changes. This characteristic is essential for the production of two-line hybrid rice systems, as it allows for controlled pollination and hybrid seed production. The TGMS trait has been extensively studied, and various TGMS lines have been developed to enhance rice breeding programs (Viraktamath and Virmani, 2001; Lee et al., 2005; Fan and Zhang, 2017; Sun et al., 2021b; Yan et al., 2024). 2.2 Molecular mechanisms underlying temperature regulation The molecular mechanisms underlying photoperiod-and-temperature regulation of P/TGMS in rice involve complex interactions between genes, microRNAs (miRNAs), and environmental factors (Figure 1) (Fan and Zhang, 2017). For instance, the TGMS locus TMS5, identified in the TGMS line Annong S-1, encodes an RNase Z, which plays a significant role in the regulation of MS. The TGMS trait of AnS-1 was found to be caused by C-to-A mutation in TMS5, resulting in a premature stop codon in the RNase ZS1 protein (Zhou et al., 2014). Remarkably, male fertility of tms5 mutant was found to be completely restored at high temperatures by knocking out OsVms1 which encodes the enzyme for cP-ΔCCA-tRNA generation (Yan et al., 2024). Additionally, miRNAs such as miR156, miR5488, and miR399 have been found to regulate male fertility by influencing various metabolic pathways, including fatty acid metabolism and lignin synthesis in anther walls (Sun et al., 2021b). These findings highlight the intricate molecular networks that govern TGMS in rice. 2.3 Case study: OsTMS6 and its role in TGMS OsTms6 is another critical gene associated with TGMS in rice. Studies have shown that the expression of OsTms6 is highly sensitive to temperature variations, and its regulation is crucial for maintaining male sterility under specific temperature conditions. For example, exposure to temperatures above 32°C for more than 8 hours can induce complete male sterility in certain indica TGMS lines, while a shorter exposure is sufficient for japonica lines (Viraktamath and Virmani, 2001). The genetic background of the rice lines also influences the expression of OsTms6, indicating the need for developing diverse TGMS lines to ensure stable sterility under varying environmental conditions (Lee et al., 2005; Liu et al., 2010). 2.4 Impact of global warming on TGMS Global warming poses a significant challenge to the stability of TGMS in rice. As global temperatures rise, the critical temperature thresholds for inducing MS may be frequently exceeded, leading to unintended fertility and reduced effectiveness of TGMS lines. This necessitates the development of TGMS lines with higher critical sterility-inducing temperatures and greater resilience to temperature fluctuations (Viraktamath and Virmani, 2001; Liu et al., 2010; Zhang et al., 2022; Lin et al., 2023 ). Furthermore, understanding the molecular mechanisms and genetic factors involved in temperature regulation can aid in breeding more robust TGMS lines that can withstand the impacts of climate change (Viraktamath and Virmani, 2001; Fan and Zhang, 2017; Sun et al., 2021b; Zhang et al., 2022; Lin et al., 2023). By integrating genetic, molecular, and environmental insights, researchers can develop innovative strategies to enhance the stability and effectiveness of TGMS lines, ensuring sustainable rice production in the face of global warming.
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