Plant synthetic biology is increasingly moving from single-gene transformation toward multigene systems that reconstruct metabolic pathways, produce valuable proteins, implement synthetic circuits, and respond to environmental inputs. However, stable multigene expression in plants is limited by failures that arise across multiple biological layers, including DNA delivery and integration, chromatin context, transcription and RNA processing, translation, protein targeting, and physiological burden. In this review, we discuss multigene expression as a context-aware and burden-aware design problem rather than a simple DNA assembly problem. We first summarize major mechanisms that destabilize transgene expression, including structural rearrangement, transcriptional and post-transcriptional gene silencing, inefficient 3’-end processing, transcriptional interference, combinatorial part effects, and metabolic burden. We then describe part-level and architecture-level strategies for improving expression stability. Finally, we highlight the need for context-aware and burden-aware validation of every introduced gene across stable events, generations, tissues, and environmental conditions.
Premature bolting under elevated temperatures is a major constraint on lettuce production because it shortens the vegetative harvest period and reduces leaf quality. Bolting, floral transition, and flowering are closely connected but distinguishable processes that are regulated by overlapping genetic and environmental factors. Recent advances in lettuce genome assemblies, super-pangenomes, population resources, multi-omics analyses, and genome editing have enabled a more integrated understanding of this complex trait. This review summarizes the genomic architecture and natural variation associated with reproductive timing, the integration of temperature with photoperiodic and stress-responsive pathways, and the hormonal and metabolic changes that support inflorescence stem elongation. Particular attention is given to phytochrome-associated variation, heat-responsive transcription factors, LsSOC1, auxin and gibberellin signaling, and carbohydrate remodeling. We further discuss how these findings can inform genome editing, marker-assisted and genomic selection, and cultivation strategies. Together, current evidence indicates that heat-induced bolting arises from coordinated environmental signal integration, reproductive commitment, and hormone-dependent stem growth rather than from a single linear thermosensory pathway.
