UC San Diego

An important part of the female reproductive tract, enclosed within the gynoecium of angiosperms such as Arabidopsis thaliana, is the transmitting tract. It is a major component of the reproduction process, as the majority of the pollen tube growth occurs in the transmitting tract tissues. The transmitting tract region fails to develop in no transmitting tract (ntt) mutants, indicating that the NTT gene is necessary for specifying the transmitting tract. NTT encodes a putative transcription factor that is specifically expressed in the transmitting tract of the developing gynoecium. Here we generated and characterized promoter-GUS fusions of NTT and a number of putative downstream targets of NTT, including HALF FILLED (HAF), At1g30795 and At1g72290. Recently, the HAF gene was also shown to encode a transcription factor that plays an important role in formation of the transmitting tract. We therefore also characterized the expression pattern of a gene that is closely related to HAF called At1g18400, because it likely has functions that are redundant with HAF. We found that all of these promoter-GUS fusions were expressed in the transmitting tract. These studies provide new insights into the possible functions of several previously uncharacterized genes and lay the foundation for future efforts aimed at dissecting the cascade of gene activity that underlies transmitting tract formation.