Molecular Plant Breeding 2024, Vol.15, No.6, 429-441 http://genbreedpublisher.com/index.php/mpb 432 Figure 2 Phenotyping mutants of CSAtarget genes (Adopted from Li et al., 2022) Image caption: A, Mutation sites in INV4 and CWIN6 genomic sequences. B, Mutation sites in SWEET5, SWEET6a, and SWEET6b genomic sequences. C, Mutation sites in MST1, STP14, and STP18 genomic sequences. D, Iodine staining of pollen grains from WT and mutant anthers. Viable pollen grains stain darkly. Scale bar, 100 μm. E, Percentage of fertile pollen grains in WT and mutant anthers. Data indicate mean ± STD of three pollen grains from each of three plants. Significant differences were assessed using Student’s t test compared with WT (**P<0.01). F-H, Soluble sugar and starch content in flag leaf (F), palea/lemma (G), and anthers (H) of WT and mutant plants. Data indicate mean ±STD of three biological replicates. Significant differences were assessed using Student’s t test compared with WT (*P < 0.05, **P < 0.01). s5 s6a s6b, sweet5 sweet6a sweet6b; SUC, sucrose; GLU, glucose; FRU, fructose; S, starch (Adopted from Li et al., 2022) 3.2 Mechanisms of light perception and signal transduction The perception of light and its subsequent signal transduction are fundamental processes in regulating PGMS in rice. Key components of the circadian clock, such as Circadian Clock-Associated 1 and Pseudo-Response Regulator (PRR95), are involved in sensing photoperiod signals in leaves, which are then weakly transduced to anthers (Li et al., 2022). The CSA gene, a MYB TF, is specifically expressed in anthers and is indispensable for sugar partitioning under long-day conditions, highlighting its role in PGMS (Wang et al., 2021). Furthermore, the small RNA osa-smR5864w, produced by the noncoding RNA P/TMS12-1, is involved in the regulation of male fertility in response to photoperiod and temperature changes (Zhou et al., 2012). 3.3 Gene networks involved in light-responsive MS Gene networks play a crucial role in mediating the effects of light on male sterility in rice. Transcriptome analyses have identified numerous differentially expressed genes (DEGs) in response to varying day lengths, with significant enrichment in transport, carbohydrate, and lipid metabolic processes, as well as phytohormone signaling pathways (Figure 3) (Sun et al., 2021a). Co-expression network analysis has revealed several hub genes, including Carbon Starved Anther and UDP-glucose pyrophosphorylase, which are strongly correlated with photoperiod sensitivity and male fertility (Sun et al., 2021a). Additionally, miRNAs such as miR156, miR5488, and miR399 have been implicated in regulating male fertility by influencing SPLs, lignin synthesis, and flavonoid metabolism pathways (Sun et al., 2021b).
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