Hua Lei, Wang Na, Stanley Susan, Donald Ruth M, Eeda Satish Kumar, Billakurthi Kumari, Borba Ana Rita, Hibberd Julian M
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, United Kingdom.
Nat Commun. 2025 Jul 31;16(1):7040. doi: 10.1038/s41467-025-62087-0.
C photosynthesis has evolved in over sixty plant lineages and improves photosynthetic efficiency by ~50%. One unifying character of C plants is photosynthetic activation of a compartment such as the bundle sheath, but gene regulatory networks controlling this cell type are poorly understood. In Arabidopsis, a bipartite MYC-MYB transcription factor module restricts gene expression to these cells, but in grasses the regulatory logic allowing bundle sheath gene expression has not been defined. Using the global staple and C crop rice, we find that the SULFITE REDUCTASE promoter is sufficient for strong bundle sheath expression. This promoter encodes an intricate cis-regulatory logic with multiple activators and repressors acting combinatorially. Within this landscape we identify a distal cis-regulatory module (CRM) activated by an ensemble of transcription factors from the WRKY, G2-like, MYB-related, DOF, IDD and bZIP families. This module is necessary and sufficient to pattern gene expression to the rice bundle sheath. Oligomerisation of the CRM and fusion to core promoters containing Y-patches allow activity to be increased 220-fold. This CRM generates bundle sheath-specific expression in Arabidopsis indicating deep conservation in function between monocotyledons and dicotyledons. In summary, we identify an ancient, short, and tuneable CRM patterning expression to the bundle sheath that we anticipate will be useful for engineering this cell type in various crop species.
C4光合作用已在六十多个植物谱系中进化出来，并将光合效率提高了约50%。C4植物的一个统一特征是对如维管束鞘等区室的光合激活，但控制这种细胞类型的基因调控网络却知之甚少。在拟南芥中，一个二元MYC-MYB转录因子模块将基因表达限制在这些细胞中，但在禾本科植物中，允许维管束鞘基因表达的调控逻辑尚未明确。利用全球主要的C4作物水稻，我们发现亚硫酸盐还原酶启动子足以在维管束鞘中实现强表达。该启动子编码一种复杂的顺式调控逻辑，有多个激活因子和抑制因子组合发挥作用。在这一格局中，我们鉴定出一个远端顺式调控模块（CRM），它被来自WRKY、G2样、MYB相关、DOF、IDD和bZIP家族的一组转录因子激活。该模块对于将基因表达模式化到水稻维管束鞘中是必要且充分的。CRM的寡聚化以及与含有Y补丁的核心启动子融合可使活性提高220倍。这个CRM在拟南芥中产生维管束鞘特异性表达，表明单子叶植物和双子叶植物在功能上有深度保守性。总之，我们鉴定出一个古老、简短且可调控的CRM，它将表达模式化到维管束鞘中，我们预计这将有助于在各种作物物种中对这种细胞类型进行工程改造。
