HBI transcription factor-mediated ROS homeostasis regulates nitrate signal transduction

Abstract

Nitrate is both an important nutrient and a critical signaling molecule that regulates plant metabolism, growth, and development. Although several components of the nitrate signaling pathway have been identified, the molecular mechanism of nitrate signaling remains unclear. Here, we showed that the growth-related transcription factors HOMOLOG OF BRASSINOSTEROID ENHANCED EXPRESSION2 INTERACTING WITH IBH1 (HBI1) and its three closest homologs (HBIs) positively regulate nitrate signaling in Arabidopsis thaliana. HBI1 is rapidly induced by nitrate through NLP6 and NLP7, which are master regulators of nitrate signaling. Mutations in HBIs result in the reduced effects of nitrate on plant growth and approximately 22% nitrate-responsive genes no longer to be regulated by nitrate. HBIs increase the expression levels of a set of antioxidant genes to reduce the accumulation of reactive oxygen species (ROS) in plants. Nitrate treatment induces the nuclear localization of NLP7, whereas such promoting effects of nitrate are significantly impaired in the hbi-q and cat2 cat3 mutants, which accumulate high levels of H2O2. These results demonstrate that HBI-mediated ROS homeostasis regulates nitrate signal transduction through modulating the nucleocytoplasmic shuttling of NLP7. Overall, our findings reveal that nitrate treatment reduces the accumulation of H2O2, and H2O2 inhibits nitrate signaling, thereby forming a feedback regulatory loop to regulate plant growth and development.

Effects of Different Nitrogen Forms and Competitive Treatments on the Growth and Antioxidant System of Wedelia trilobata and Wedelia chinensis Under High Nitrogen Concentrations

“…However, some studies have found that high N can cause oxidative damage to plants, which is consistent with our results that excessive N had toxic effects on plants. Plants activate various defense mechanisms, including increasing antioxidant enzyme activities to enhance stress tolerance ( Chu et al, 2021 ). We also found that the exotic plant W. trilobata had more adaptability to excessive N than W. chinensis , mainly through promoting its growth and antioxidant enzyme activities.…”

“…Heavy metals are toxic to plants; however, the addition of N in different forms can enhance plant tolerance to heavy metals through an improved antioxidant defense system. However, it is also well established that high N can cause oxidative damage to crop plants ( Chu et al, 2021 ). Therefore, the optimization of N rates, particularly when applying in different forms, is essential to reduce the damage caused by oxidative stress under high N ( Chen et al, 2020 ).…”

The NIN-LIKE PROTEIN 7 (NLP7) transcription factor modulates auxin pathways to regulate root cap development

“…Together, our data lead to a model in which NLP7 regulates root cap cell release and cell production by impacting the expression of auxin carriers and transcription factors critical for root cap development (Figure 9). NLP7 is not transcriptionally regulated by NO 3 - (Castaings et al, 2009), but in conditions with sufficient nitrate, NLP7 protein is retained in the nucleus (Marchive et al, 2013; Karve et al, 2016; Liu et al, 2017; Chu et al, 2021). In these conditions, in wild type plants, NLP7 promotes expression of PILS3, which reduces the nuclear auxin responses in the last layer of the root cap and may contribute to an auxin minima in the last layer of the root cap.…”

“…NLP7 protein is present in the cytoplasm in nitrate-free conditions and is retained in the nucleus upon exposure to nitrate (Marchive et al, 2013; Liu et al, 2017; Chu et al, 2021). Consistent with cytoplasmic localization of NLP7 in nitrate-free conditions, in wild type plants under nitrate-free conditions, PILS3 expression is repressed (Supplemental Figure S2).…”

BRASSINAZOLE RESISTANT 1 Mediates Brassinosteroid-Induced Calvin Cycle to Promote Photosynthesis in Tomato

“…In addition, carbon and nitrogen metabolism in plants are interconnected. Recently, BR signaling was shown to impinge on the nitrate response pathway ( Chu et al, 2021 ). It is unclear whether nitrogen metabolism is involved in BR-mediated increase in photosynthesis.…”