Table_1_FITNESS Acts as a Negative Regulator of Immunity and Influences the Plant Reproductive Output After Pseudomonas syringae Infection.DOC

Plants, as sessile organisms, are continuously threatened by multiple factors and therefore their profitable production depends on how they can defend themselves. We have previously reported on the characterization of fitness mutants which are more tolerant to environmental stresses due to the activation of defense mechanisms. Here, we demonstrate that in fitness mutants, which accumulate moderate levels of salicylic acid (SA) and have SA signaling activated, pathogen infection is restricted. Also, we demonstrate that NPR1 is essential in fitness mutants for SA storage and defense activation but not for SA synthesis after Pseudomonas syringae (Pst) infection. Additionally, these mutants do not appear to be metabolically impared, resulting in a higher seed set even after pathogen attack. The FITNESS transcriptional network includes defense-related transcription factors (TFs) such as ANAC072, ORA59, and ERF1 as well as jasmonic acid (JA) related genes including LIPOXYGENASE2 (LOX2), CORONATINE INSENSITIVE1 (COI1), JASMONATE ZIM-domain3 (JAZ3) and JAZ10. Induction of FITNESS expression leads to COI1 downregulation, and to JAZ3 and JAZ10 upregulation. As COI1 is an essential component of the bioactive JA perception apparatus and is required for most JA-signaling processes, elevated FITNESS expression leads to modulated JA-related responses. Taken together, FITNESS plays a crucial role during pathogen attack and allows a cost-efficient way to prevent undesirable developmental effects.

植物作为固着生物，持续面临多种胁迫因素的威胁，因此其高效生产依赖于自身的防御能力。我们此前曾报道过一类适合度突变体（fitness mutants）的特征：这类突变体因防御机制激活而对环境胁迫具备更强耐受性。本研究证实，在这类积累适度水平水杨酸（salicylic acid, SA）且SA信号通路被激活的适合度突变体中，病原菌侵染受到抑制。此外，本研究还证实，在丁香假单胞菌（Pseudomonas syringae, Pst）侵染后，病程相关基因非表达子1（NPR1）对于适合度突变体中的SA储存与防御激活至关重要，但并不参与SA的合成过程。此外，这类突变体并未出现代谢损伤，即便在病原菌侵染后，仍能产生更多的种子。FITNESS基因的转录调控网络包含多种防御相关转录因子（transcription factors, TFs），如ANAC072、ORA59与ERF1，同时还涉及茉莉酸（jasmonic acid, JA）相关基因，包括脂氧合酶2（LIPOXYGENASE2, LOX2）、CORONATINE INSENSITIVE1（COI1）、茉莉酸ZIM结构域蛋白3（JASMONATE ZIM-domain3, JAZ3）以及JAZ10。诱导FITNESS基因的表达会导致COI1表达下调，同时使JAZ3与JAZ10表达上调。由于COI1是活性JA感知复合体的核心组分，且参与绝大多数JA信号通路过程，因此FITNESS表达水平升高会调控JA相关的应答反应。综上，FITNESS基因在病原菌侵染过程中发挥关键作用，且可通过一种成本效益最优的方式，避免植株产生不良的发育效应。