ANK6, a mitochondrial ankyrin repeat protein, is required for male-female gamete recognition in Arab.pdf

ANK6, a mitochondrial ankyrin repeat protein, is required for male-female gamete recognition in Arabidopsis thaliana Feng Yua,1, Jia Shia,1, Jiye Zhoua,1, Jianing Gua, Qihui Chena, Jian Lia, Wei Chenga, Dandan Maoa, Lianfu Tiana, Bob B. Buchananb,2, Legong Lic, Liangbi Chena, Dongping Lia,2, and Sheng Luana,b,2 aCollege of Life Sciences, Hunan Normal University, Changsha 410081, People’s Republic of China; bDepartment of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and cCollege of Life Sciences, Capital Normal University, Beijing 100037, People’s Republic of China Contributed by Bob B. Buchanan, October 29, 2010 (sent for review June 21, 2010) Double fertilization in angiosperms involves several successive steps, including guidance and reception of the pollen tube and male-female gamete recognition. Each step entails extensive communication and interaction between two different reproduc- tive cell or tissue types. Extensive research has focused on the pollen tube, namely, its interaction with the stigma and reception by maternal cells. Little is known, however, about the mechanism by which the gametes recognize each other and interact to form a zygote. We report that an ankyrin repeat protein (ANK6) is essential for fertilization, specifically for gamete recognition.ANK6 (At5g61230) was highly expressed in the male and female game- tophytes before and during but not after fertilization. Genetic anal- ysis of a T-DNA insertional mutant suggested that loss of function of ANK6 results in embryonic lethality. Moreover, male-female gamete recognition was found to be impaired only when an ank6 male gamete reached an ank6 female gamete, thereby preventing formation of homozygous zygotes. ANK6 was localized to the mi- tochondria, where it interacted with SIG5, a transcription initiation factor previously found to be essential for fertility. These results show that ANK6 plays a central role in male-female gamete recog- nition, possibly by regula