cis- and trans-elements for the transcriptional regulation of sugar responsive genes: from current knowledge to future applications.

Sugar metabolism in plants is highly dynamic throughout their life cycle, driven by the continuous production, accumulation, and distribution of these molecules along the plant body. To cope with fluctuating sugar levels during their life cycle, plants have developed mechanisms to sense and respond to these changes accordingly. Noteworthy, sugars not only fulfill metabolic roles, but also act as signaling molecules that regulate plant growth and development. Of the array of sugar responses, their influence on gene expression is particularly significant, as it impacts a wide range of physiological processes, including key economic traits of plants. However, despite the broad regulatory role of sugars in gene expression, the transcriptional mechanisms behind their regulation remain largely unknown. Among the many sugar-regulated genes in plants, efforts have been focused on identifying cis-regulatory elements (CREs) and trans-regulatory factors (transcription factors, TFs) involved in gene sugar responsiveness at transcriptional level, but only some have been experimentally confirmed. Therefore, this review outlines those approaches used for identifying sugar CREs and TFs, along with an updated compilation of the elements associated with glucose and sucrose signaling transcriptional responses. In addition, the evolutionary conservation of these regulatory elements in different plant species is addressed, highlighting those with potential biotechnological applications. In summary, the gathering of this information has the purpose of updating our current knowledge regarding the mechanism of how sugars exert its effect on gene expression. This understanding is essential for advancing in the manipulation of these regulatory elements to improve key traits in economically valuable plants, such as oil and sugar accumulation, crop yield, and fruit quality.