Paraquat is one of the most widely used herbicides in the world. However, no paraquat transporter has been isolated in plants. Here, we describe paraquat‐tolerant mutant pqt24‐1, isolated from an ...activation‐tagging library on the basis of its tolerance to 2 μm paraquat in the seedling stage. Molecular analysis revealed that the T‐DNA was inserted in the 13th exon of At1g66950, which encodes AtPDR11, a member of the ATP‐binding cassette transporter superfamily. As a result, AtPDR11 was knocked out in the mutant. Loss‐of‐function mutations of AtPDR11 led to reduced paraquat accumulation in plant cells. In addition, the AtPDR11 protein was specifically localized in the plasmalemma, suggesting AtPDR11 as a potential transporter of paraquat. This conclusion was supported by kinetic analysis of paraquat import. Further studies showed that the transcript level of AtPDR11 could be strongly induced by paraquat and other abiotic stresses including H2O2, indicating possible up‐regulation of AtPDR11 expression by oxidative stress signaling. Thus, our data suggest that paraquat is an opportunistic substrate of AtPDR11 and the enhanced paraquat tolerance of pqt24‐1 is due to reduced uptake of paraquat into plant cells.
Drought and salinity are two major environmental factors limiting crop production worldwide. Improvement of drought and salt tolerance of crops with transgenic approach is an effective strategy to ...meet the demand of the ever‐growing world population. Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a homeodomain‐START transcription factor, has been demonstrated to significantly improve drought tolerance in Arabidopsis, tobacco, tall fescue and rice. Here we report that AtHDG11 also confers drought and salt tolerance in upland cotton (Gossypium hirsutum) and woody plant poplar (Populus tomentosa Carr.). Our results showed that both the transgenic cotton and poplar exhibited significantly enhanced tolerance to drought and salt stress with well‐developed root system. In the leaves of the transgenic cotton plants, proline content, soluble sugar content and activities of reactive oxygen species‐scavenging enzymes were significantly increased after drought and salt stress compared with wild type. Leaf stomatal density was significantly reduced, whereas stomatal and leaf epidermal cell size were significantly increased in both the transgenic cotton and poplar plants. More importantly, the transgenic cotton showed significantly improved drought tolerance and better agronomic performance with higher cotton yield in the field both under normal and drought conditions. These results demonstrate that AtHDG11 is not only a promising candidate for crops improvement but also for woody plants.
Improvement of crop drought resistance and water-use efficiency (WUE) has been a major endeavor in agriculture. Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a ...homeodomain-START transcription factor we previously identified from the enhanced drought tolerance1 mutant (edt1), has been demonstrated to improve drought tolerance and WUE significantly in multiple plant species when constitutively overexpressed.
Here, we report the genetic evidence suggesting a genetic pathway, which consists of EDT1/HDG11, ERECTA, and E2Fa loci, and regulates WUE by modulating stomatal density. AtEDT1/HDG11 transcriptionally activates ERECTA by binding to homeodomain-binding (HD) cis-elements in the ERECTA promoter. ERECTA, in turn, depends on E2Fa to modulate the expression of cell cycle-related genes.
This modulation affects the transition from mitosis to endocycle, leading to increased ploidy levels in leaf cells, and therefore increased cell size and decreased stomatal density.
Our results suggest a possible EDT1/HDG11-ERECTA-E2Fa genetic pathway that reduces stomatal density by increasing cell size and provide a new avenue to improve WUE of crops.
Summary
Sessile plants constantly experience environmental stresses in nature. They must have evolved effective mechanisms to balance growth with stress response. Here we report the MADS‐box ...transcription factor AGL16 acting as a negative regulator in stress response in Arabidopsis.
Loss‐of‐AGL16 confers resistance to salt stress in seed germination, root elongation and soil‐grown plants, while elevated AGL16 expression confers the opposite phenotypes compared with wild‐type. However, the sensitivity to abscisic acid (ABA) in seed germination is inversely correlated with AGL16 expression levels.
Transcriptomic comparison revealed that the improved salt resistance of agl16 mutants was largely attributed to enhanced expression of stress‐responsive transcriptional factors and the genes involved in ABA signalling and ion homeostasis. We further demonstrated that AGL16 directly binds to the CArG motifs in the promoter of HKT1;1, HsfA6a and MYB102 and represses their expression. Genetic analyses with double mutants also support that HsfA6a and MYB102 are target genes of AGL16.
Taken together, our results show that AGL16 acts as a negative regulator transcriptionally suppressing key components in the stress response and may play a role in balancing stress response with growth.
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 ∼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.
Plants frequently suffer from environmental stresses in nature and have evolved sophisticated and efficient mechanisms to cope with the stresses. To balance between growth and stress response, plants ...are equipped with efficient means to switch off the activated stress responses when stresses diminish. We previously revealed such an off‐switch mechanism conferred by Arabidopsis PARAQUAT TOLERANCE 3 (AtPQT3) encoding an E3 ubiquitin ligase, knockout of which significantly enhances resistance to abiotic stresses. To explore whether the rice homologue OsPQT3 is functionally conserved, we generated three knockout mutants with CRISPR‐Cas9 technology. The OsPQT3 knockout mutants (ospqt3) display enhanced resistance to oxidative and salt stress with elevated expression of OsGPX1, OsAPX1 and OsSOD1. More importantly, the ospqt3 mutants show significantly enhanced agronomic performance with higher yield compared with the wild type under salt stress in greenhouse as well as in field conditions. We further showed that OsPQT3 expression rapidly decreased in response to oxidative and other abiotic stresses as AtPQT3 does. Taken together, these results show that OsPQT3 is functionally well conserved in rice as an off‐switch in stress response as AtPQT3 in Arabidopsis. Therefore, PQT3 locus provides a promising candidate for crop improvement with enhanced stress resistance by gene editing technology.
OsPQT3, a rice homologue of Arabidopsis PQT3 encoding an E3 ubiquitin ligase, is functionally conserved in rice. Like AtPQT3, OsPQT3 negatively regulates stress resistance. Knockout of OsPQT3 locus confers stress resistance, providing a promising candidate for crop improvement with enhanced stress resistance by gene editing technology.
Jasmonic acid (JA) is well known to promote lateral root formation but the mechanisms by which JA signalling is integrated into the pathways responsible for lateral root formation, and how it ...interacts with auxin in this process remains poorly understood. Here, we report that the highly JA-responsive ethylene response factor 109 (ERF109) mediates cross-talk between JA signalling and auxin biosynthesis to regulate lateral root formation in Arabidopsis. erf109 mutants have fewer lateral roots under MeJA treatments compared with wild type whereas ERF109 overexpression causes a root phenotype that resembles those of auxin overproduction mutants. ERF109 binds directly to GCC-boxes in the promoters of ASA1 and YUC2, which encode two key enzymes in auxin biosynthesis. Thus, our study reveals a molecular mechanism for JA and auxin cross-talk during JA-induced lateral root formation.
Abstract
Nitrogen (N) is indispensable for crop growth and yield, but excessive agricultural application of nitrogenous fertilizers has generated severe environmental problems. A desirable and ...economical solution to cope with these issues is to improve crop nitrogen use efficiency (NUE). Plant NUE has been a focal point of intensive research worldwide, yet much still has to be learned about its genetic determinants and regulation. Here, we show that rice (Oryza sativa L.) NIN-LIKE PROTEIN 1 (OsNLP1) plays a fundamental role in N utilization. OsNLP1 protein localizes in the nucleus and its transcript level is rapidly induced by N starvation. Overexpression of OsNLP1 improves plant growth, grain yield, and NUE under different N conditions, while knockout of OsNLP1 impairs grain yield and NUE under N-limiting conditions. OsNLP1 regulates nitrate and ammonium utilization by cooperatively orchestrating multiple N uptake and assimilation genes. Chromatin immunoprecipitation and yeast one-hybrid assays showed that OsNLP1 can directly bind to the promoter of these genes to activate their expression. Therefore, our results demonstrate that OsNLP1 is a key regulator of N utilization and represents a potential target for improving NUE and yield in rice.
OsNLP1 rapidly responds to N availability, enhances N uptake and assimilation, providing great potential for breeding rice cultivars with high yield and NUE under N-limiting conditions
Summary
Plants play a prominent role as sulfur reducers in the global sulfur cycle. Sulfate, the major form of inorganic sulfur utilized by plants, is absorbed and transported by specific sulfate ...transporters into plastids, especially chloroplasts, where it is reduced and assimilated into cysteine before entering other metabolic processes. How sulfate is transported into the chloroplast, however, remains unresolved; no plastid‐localized sulfate transporters have been previously identified in higher plants. Here we report that SULTR3;1 is localized in the chloroplast, which was demonstrated by SULTR3;1‐GFP localization, Western blot analysis, protein import as well as comparative analysis of sulfate uptake by chloroplasts between knockout mutants, complemented transgenic plants, and the wild type. Loss of SULTR3;1 significantly decreases the sulfate uptake of the chloroplast. Complementation of the sultr3;1 mutant phenotypes by expression of a 35S‐SULTR3;1 construct further confirms that SULTR3;1 is one of the transporters responsible for sulfate transport into chloroplasts.
Summary
Sulfur (S) is an essential macronutrient for plants and a signaling molecule in abiotic stress responses. It is known that S availability modulates root system architecture; however, the ...underlying molecular mechanisms are largely unknown.
We previously reported an Arabidopsis gain‐of‐function mutant sulfate utilization efficiency4 (sue4) that could tolerate S deficiency during germination and early seedling growth with faster primary root elongation. Here, we report that SUE4, a novel plasma membrane‐localized protein, interacts with the polar auxin transporter PIN1, resulting in reduced PIN1 protein levels and thus decreasing auxin transport to the root tips, which promotes primary root elongation.
Moreover, SUE4 is induced by sulfate deficiency, consistent with its role in root elongation. Further analyses showed that the SUE4–PIN1 interaction decreased PIN1 levels, possibly through 26 S proteasome‐mediated degradation.
Taken together, our finding of SUE4‐mediated root elongation is consistent with root adaptation to highly mobile sulfate in soil, thus revealing a novel component in the adaptive response of roots to S deficiency.
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