阿拉伯芥之油菜素類固醇透過 BZR1 調控缺氮下花青素之累積篩選參與抗病反應之阿拉伯芥 NPF 轉運蛋白突變株

Abstract

Nitrogen (N) limitation inhibits plant growth and development, leading to plant evolves diverse ways to adapt it. Most researches revealed that plant could modify the root architecture via hormone as a signal to resist N limitation. Nevertheless, the regardless of shoot researches let the shoot part still obscure. Even though anthocyanin accumulation in shoot have been proven which is one of the important strategy to challenge N limitation, the mechanism and signaling are still not elucidated. Here, through reverse genetics, screening of stress-related hormone mutants, the results exhibited that brassinosteroid (BR) biosynthesis and receptor were necessary for anthocyanin production under N limitation. The master transcription factor of BR signaling, BZR1, was then identified as the key hub for anthocyanin production by inhibiting anthocyanin repressors, LBD37 and LBD38, directly. Meanwhile, BR is also required for the biomass maintaining to N limitation by maintaining more biomass. Our investigation propose a model explaining how BR involves in plant nitrogen uptakes and utilizations. In conclusion, our research validated that BR is a key hormone for plant anthocyanin production; for plant biomass maintaining under N limitation, especially in shoot. NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER family (NPF) has been reported to involve in plant physiological functions through mediating distribution of various substrates. Although the functions of these proteins have been studied, the roles of NPF transporters upon biotic stresses remain unclear. In this study, we first analyzed the transcription level of all 53 genes in NPF family upon pathogen infection from BAR microarray database (e-Northerns w. Expression Browser), and 17 NPF genes showed altered expression patterns. After the pathogenicity test by Pst DC3000 infection, some NPF mutants showed different responses compared to wild-type plants. Two genes were selected to study further, which are NRT1.5/NPF7.3, PTR3/NPF5.2, The nrt1.5/npf7.3 mutants showed more susceptibility to Pst DC3000, suggesting that NRT1.5/NPF7.3 which mediates root-to-shoot nitrate transport is required for plant resistance to Pst DC3000. In addition, the transcription level of NRT1.5/NPF7.3 is induced by both Pst DC3000 and Flg22. Whether root-to-shoot nitrate transport by NRT1.5/NPF7.3 enhances the plant defense responses will be further investigated. The expression of PTR3/NPF5.2, a dipeptide transporter, is induced by Pst DC3000, Flg22, and salicylic acid (SA). Although PTR3 has no effect on local defense responses, the two ptr3 T-DNA insertion mutants lost the systemic acquired resistance (SAR) to Pst DC3000. What is the role of PTR3/NPF5.2 in SAR will be analyzed. Taken together, transport activity of NPF proteins is not only important for nutrient distribution, but also participates in adjust physiological responses upon biotic stresses. However, the detailed functions of how NPF transporters are able to resist pathogen need further examination.