Moleculer bilogical study of origin and evolution of outer integument

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13640692
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 系統・分類
• Research Institution: Chiba University
• Principal Investigator: UEHARA Koichi Chiba Univesity, Faculty of Horticulture, Assistant Professor, 園芸学部, 助手 (20221799)
• Co-Investigator(Kenkyū-buntansha): ITO Motomi University of Tokyo, Graduate school of Arts and Sciences, Associate Professor, 大学院・総合文化研究科, 助教授 (00193524)
• Project Period (FY): 2001 – 2002
• Keywords: outer integument / YABBY gene family / INNER NO OUTER / adaxial-abaxial polarity / Nymphaeaceae / angiosperm / ovule / in situ hybridization

Research Abstract

Carpels, double fertilization, and outer integument of the two integuments are characteristics of Angiosperms. These origin are connected with the early evolution of angiosperms. The YABBY gene family is known in Arabidopsis which participates in the formation of carpel and outer integument. Most of YABBY gene family perticipate in the control of adaxial-abaxial polarity of plant organs. INO (INNER NO OUTER) of YABBY gene family express outer integument of Arabidopsis thaliana. In ino mutants the growth of the outer integument is aborted or limited. This suggests the INO is concerned with the development and morphology of outer integument. In A. thaliana, the ovules are anatropous and have a polarity along the adaxial - abaxial axis, which is expressed in the asymmetrical formation and growth of the outer integument. This shows that the adaxial-abaxial polarity exists in the outer integument of A. thaliana. Recent molecular phylogenetic analyzes show that Amborellaceae is branched at t he base of angiosperms, followed by Nymphaeaceae. In Nymphaeaceae there are various types of ovules including anatropous ovules, hemianatropous ovules, and orthotropous ovules. To understand better the homology and evolution of the outer integument, it is useful to examine whether there is an adaxial-abaxial polarity even in the outer integument of basal angiosperms such as Nymphaeaceae. Our purpose is to isolate homologues of INO and YABBY gene families from Nymphaeaceae and examined the expression pattern of INO homologue in Nymphaeaceae. We isolated 3 homologues of YABBY gene family form B.S (FIL, YAB2, INO), two from Cabomba (FIL, YAB2), one from N.j (FIL). and Nymphaea alba (INO), N. colorata (INO). In in situ hybridization analysis, NaINO (Nymphaea alba) is expressed exclusively in the outer layer (epidermis) of the outer integument, as in Arabidopsis thaliana. This indicates that a similar adaxial-abaxial pattern is present in the outer integument of N. alba. This supports the hypothesis that the outer integument is homologous with a leaf and retains adaxial-abaxial identity.