The Arabidopsis thaliana NGATHA1 transcription factor acts as a promoter of a general differentiation program and a carpel identity factor

The Arabidopsis thaliana NGATHA (NGA) family is a four-membered subclade of the B3-type transcription factor superfamily, and plays an essential role in the style development. NGAs also act as negative regulators of cell proliferation in leaf and petal growth. The notion that NGAs might act as promoters of a general differentiation program has been proposed to explain the involvement of NGAs in these seemingly discrete functions. Here, we tested this notion by activating NGA1 transcription in the expression domains of Arabidopsis thaliana Meristem Layer 1, AINTEGUMENTA, SHOOTMERISTEMLESS, CLAVATA3 (CLV3), and WUSCHEL (WUS), where cells remain mostly undifferentiated and pluripotent. We found that those specific cells expressing NGA1 lost their meristematic competence, becoming terminally differentiated. We also found that the inflorescence meristems of the plants expressing NGA1 in the CLV3 domain failed to develop floral meristems and differentiated into a terminal carpeloid cylinder without any other floral organs; similarly, the floral meristems of the plants expressing NGA1 in the WUS domain all developed into carpeloid cylinders with no other floral organs. Our results not only support the notion that NGA1 seems to be a promoter of a general differentiation program, but also raise the possibility that NGA1 may act as a carpel identity factor.