Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2013
Publication Date: 11/13/2013
Citation: Zhang, J., Yan, G., Wen, Z., An, Y., Singer, S., Liu, Z. 2013. Two tobacco AP1-like gene promoters with highly specific, tightly regulated and uniquely expressed activity during floral transition, initiation and development. Planta. 239:469-478. Interpretive Summary: Biotech engineering requires diverse highly specific and tightly regulated promoters for manipulating gene function and agronomic traits. However, very few promoters with the desired regulatory features are available. In this study, we isolated and characterized two flower-specific promoters and found that they are capable of generating irreversible sterility which could be used for prevention of transgene flow, biomass production and flower architecture and structure. This work provides new biotech resources for directing and engineering gene function in fruit and other crops.
Technical Abstract: Biotech engineering of agronomic traits requires an array of highly specific and tightly regulated promoters in flower or other tissues. In this study, we isolated and characterized two tobacco AP1-like promoters (termed NtAP1La and NtAP1Lb1) in transgenic plants using GUS reporter and tissue-specific ablation analyses. Our results show that two promoters are active in florally determined inflorescence but not in apical vegetative meristem and tissue, as reflected by strong GUS staining in and DT-A-mediated ablation of apical shoot tips exclusively during or at vegetative to reproduction transition stage. We also show that NtAP1Lb1 is stronger and more active than NtAP1La in inflorescence because the former gave a high tissue ablation frequency and stronger phenotype compared to the latter. We further reveal that two promoters are uniformly expressed in floral meristem of stage one and two floral buds but differentially expressed in floral organs in later stages, with NtAP1La active only in carpels from stage four to five and NtAP1Lb1 in all floral organs from stage three to seven. Interestingly, their activity in floral organs changes during floral development, with NtAP1La activity gradually confined to ovary tissue from stage nine onward while NtAP1Lb1 completely absent in all floral organs from stage 11 onward, indicating that both promoters are differentially regulated in a flower development-dependent manner. Evidently, two promoters acquire similar but distinct inflorescence-, floral meristem-, and floral organ-, specific, and development-dependent regulatory features without any leaky activity in vegetative tissues. These features are novel and rarely observed in other flower-specific promoters. Potential application of these promoters for engineering sterility, biomass production and flower architecture as well as flower-specific transgene excision will be discussed.