Plant Gene and Trait 2025, Vol.16, No.3, 92-103 http://genbreedpublisher.com/index.php/pgt 98 Water conditions cannot be ignored. Once the water supply is insufficient or extreme temperature differences are encountered, stomatal conductance, Rubisco activity, light system repair, etc. will “fall off the chain”, and these adjustments are often completed by transcription factors such as MYB, bZIP, and DREB (Saibo et al., 2009). 7.2 Stage-specific expression of photosynthesis-related genes Gene expression is not a “static” thing, especially those genes related to photosynthesis, which show strong dynamics in different growth stages and environmental conditions. Take the seedling stage as an example. When plants just “open their eyes” from the darkness, light signals and temperature signals have begun to cooperate, and through regulatory mechanisms such as the HY5-PIF module, they step by step promote the activation of genes for chlorophyll and carotenoid synthesis. This is the key stage for them to switch from dependence to autotrophy (Toledo-Ortiz et al., 2014). However, in addition to rapid responses, there are also some “slow variables” at work. The acquisition of traits such as stress tolerance often depends on the long-term maintenance of transcriptional states, which is closely related to the gene expression memory mechanism we are familiar with (Jarad et al., 2020). What’s more complicated is that the nuclear genome and the chloroplast genome must maintain communication, and they use anterograde and retrograde signals to ensure that the expression rhythm matches the developmental and environmental needs (Berry et al., 2013). 7.3 Hormonal signaling pathways regulating photosynthetic capacity When plants cope with environmental stress, they rely not only on regulation at the gene level, but also on hormone signals as another “central control system”. Hormones such as abscisic acid (ABA) and auxin not only regulate gene expression, but also act as “indirect promoters” of photosynthetic capacity. Especially in the context of strong light or low temperature, the synthesis and signal transduction of ABA will follow the environment and activate a group of genes related to protection and adaptability in a timely manner (Soitamo et al., 2008). Transcription factors such as PIF4 and SEUSS (SEU) are like “translators” who are responsible for integrating light, temperature and hormone signals together and then transmitting them to downstream synthesis or response genes, thereby affecting plant growth and photosynthesis (Huai et al., 2018; Huang et al., 2019). These hormone pathways do not operate alone, they will “negotiate” with external environmental conditions to ultimately fine-tune the photosynthetic efficiency and adversity adaptability of plants. 8 Case Study: Gene Regulation and Yield Performance in Elite Sugarcane Varieties 8.1 Identification of high-expression C4 gene clusters in commercial hybrids Not all genes that have been preserved have become the protagonists, but in the evolution of C4 plants, a group of genes that were originally expressed at high levels in ancestral non-C4 plants later became the “main force” of the C4 pathway in modern sugarcane hybrids. In this type of gene cluster, in addition to familiar faces such as PEPC, PPDK, and NADP-ME, other members involved in light response, sugar metabolism, transcriptional regulation, and metabolite transport can also be seen (Moreno-Villena et al., 2017). Their high expression in leaves is not accidental, and it is likely that they are “going with the flow” in the process of forming and strengthening the C4 cycle. In breeding practice, the expression levels of these genes have gradually been “pushed up”, and many excellent varieties have come to the forefront thanks to them. 8.2 Correlation between gene expression profiles and photosynthetic rates under field conditions Performance in the greenhouse is certainly important, but the field is the “real battlefield”. Many studies have found that under actual planting conditions, there is a clear relationship between those C4-related metabolic enzyme genes - once the expression level is increased - and the improvement of photosynthetic capacity. For example, in hybrids of corn and sorghum, the expression of key enzymes such as carbon assimilation enzymes can even exceed that of the parents. This “non-additive” expression is often accompanied by a simultaneous increase in net photosynthetic rate, stomatal conductance, and transpiration rate, and it can indeed be reflected in grain weight and total biomass (Li et al., 2020). These data are actually illustrating a problem: when looking at photosynthetic efficiency and yield, you might as well start with the expression spectrum, which may be a very reliable “early warning system” (Zhao et al., 2024).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==