Distinguished by the pattern of the distribution of blades on the petiole, leaves have two basic types: simple and compound. Simple leaves comprise a single blade, but compound leaves have multiple blade units and exhibit more complex and diverse patterns of organ organization. 

The molecular mechanisms underlying their pattern formation of compound leaves are receiving more and more attention in recent years. Studies in model legume Medicago truncatula have led to an improved understanding of the genetic control of the compound leaf patterning. 

In a study published in Frontiers in Plant Science, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) summarizethe current knowledge about how the leaf morphogenesis of M. truncatula is regulated by the coordination of genetic factors, hormones, and other signals, and finally to pattern the compound leaf. 

The researchers mainly dissect the regulators and pathways controlling the primary morphogenesis of the compound leaf in M. truncatula, with a particular concern about the mechanisms responsible for the pattern formation. 

They show that one of the most critical developmental processes that determine the trifoliate leaf pattern is the formation of three separated leaflet primordia during early stages, which is characterized by two key events: the initiation of leaflet primordia and the boundary formation between leaflets. 

They also compare the molecular mechanisms between leaf development of different model species. They summarize that the LFY/SGL1 pathway plays a central role in maintaining the morphogenetic activity of the compound leaf primordia. The leaflet initiation and outgrowth is tightly associated with the auxin pathway. The boundary formation between leaflets is critically dependent on the function of the boundary-specific MtNAM/MtCUC2 gene and the FCL1 gene. Moreover, the adaxial–abaxial polarity genes play important roles in determining the compound leaf pattern. 

“We hope that our review will provide better understanding for future studies on legume plants and their utilization prospects,” said CHEN Jianghua, principal investigator of the study. 

Contact 

CHEN Jianghua  Ph.D Principal Investigator       

Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China  

E-mail: jhchen@xtbg.ac.cn