| This thesis describes the characterization of two new transposable element (TE) families, Mx-rMx, a member of the hAT superfamily, and Jittery, a member of the Mutator superfamily in maize (Zea mays). In addition, the transposon Ac-tagged mutations aberrant pollen transmission 1 (apt1) and necrotic upper tips (nut1) were analyzed.; First, the autonomous TE Mx (M&barbelow;obile element induced by x&barbelow;-rays) and its partner 571-bp rMx (r&barbelow;esponder to Mx) were isolated and genetically characterized based on the bz-x3m mutation. Mx is 3731 bp long, ends in 13 bp terminal inverted repeats (TIRs) and causes an 8-bp target site duplication (TSD). Mx is predicted to encode an Ac-like transposase and does not interact with Ac. Second, Jittery (Jit), another autonomous TE, was isolated and genetically characterized based on the bz-m039 mutation. Jit is 3.9-kb long, ends in 181 bp TIR, and causes a 9-bp TSD. Compared with other homologues in B73 and its source AR stock, Jit might have lost 4-bp at the 3' end. Jit is predicted to encode a MURA-like transposase. Jit does not leave footprints upon excision or reinsert in the genome. The loss of 4-bp at the 3' end of Jit may account for its failure to reinsert in the genome.; Two Ac-tagged mutations apt1 and nut1 were also characterized. The apt1 mutation causes defective male transmission. As a heterozygote, apt1(Ac) is an efficient system for selecting Ac transpositions. The apt1 mutant shows twisted and short pollen tubes. The APT1 protein is homologous to SABRE and KIP in Arabidopsis. APT1 localizes to the Golgi body in growing pollen tubes, suggesting that it may be involved in membrane trafficking in pollen tubes.; Finally, the Ac-tagged nut1 mutant displays necrotic tips in the upper leaves and the tassel, reduces the size of tassel inflorescences, and causes a small plant. The nut1 gene encodes a protein highly homologous to the NAC protein. nut1 expresses in the shoot apex and tassel, suggesting that it controls meristem identity and maintains tassel inflorescence structure. Given its function in necrosis, meristem development and plant size, the nut1 gene can be of importance for cross-talk between different pathways. |
