第1226回生物科学セミナー
The making of elaborate petals in Nigella (Ranunculaceae)
Hongzhi Kong（Chinese Academy of Sciences, Beijing 100093, China）
2018年07月11日(水) 10:30-12:00 理学部2号館 223号室
As a special type of floral organs, petals show tremendous diversity in shape, structure, color/coloration and function, and have increasingly been used as a model for the study of plant organ evolution. Petals of Nigella (Ranunculaceae) are of particular interest because they form highly elaborate, bilabiate structures with extensive modifications. To understand how Nigella petals have become elaborate and diverse, we first investigated the morphology, micro-morphology and development of Nigella petals. We found that the degree of petal complexity increase gradually during the evolution of the genus, likely through modification of pre-existing characters (e.g., the elongation of stalk and the alteration of the upper and lower lips in shape) as well as de novo origination of new features (e.g., pseudonectaries, short trichomes, and conical cells). By conducting extensive digital gene expression (DGE) analyses, we further identified the genes that play key roles in the elaboration and diversification of Nigella petals. We found that: 1) changes in the expression domains of adaxial/abaxial polarity genes may have led to the formation of the upper lip; 2) ectopic expression of LMI1, a class I HD-Zip family transcription factor gene, may be responsible for the bifurcation of the lower lip; and 3) YAB5-1, a YABBY family transcription factor gene, is involved in the formation of pseudonectaries and short trichomes. There results confirmed that Nigella is an excellent model for the study of petal elaboration and pave the way for better understanding the basics and underlying mechanisms of plant organ diversification.
