Journal of Experimental Botany最新文献

Phosphorus is an essential nutrient for all crops. Thus, a better understanding of the genetic control of phosphorus use efficiency evident in physiological, developmental, and morphological traits and its environmental plasticity is required to establish the basis for maintaining or enhancing yield while making agriculture more sustainable. In this study, we utilized a diverse panel of maize (Zea mays L.), including 398 elite and landrace lines, phenotyped across three environments and two phosphorus fertilization treatments. We performed genome-wide association mapping for 13 traits, including phosphorus uptake and allocation, that showed a strong environment dependency in their expression. Our results highlight the complex genetic architecture of phosphorus use efficiency as well as the substantial differences between the evaluated genetic backgrounds. Despite harboring more of the identified quantitative trait loci, almost all of the favorable alleles from landraces were found to be present in at least one of the two elite heterotic groups. Notably, we also observed trait-specific genetic control even among biologically related characteristics, as well as a substantial plasticity of the genetic architecture of several traits in response to the environment and phosphorus fertilization. Collectively, our work illustrates the difficulties in improving phosphorus use efficiency, but also presents possible solutions for the future contribution of plant breeding to improve the phosphorus cycle.

Heat stress adversely impacts plant growth, development, and grain yield. Heat shock factors (Hsf), especially the HsfA2 subclass, play a pivotal role in the transcriptional regulation of genes in response to heat stress. In this study, the coding sequence of maize ZmHsf17 was cloned. ZmHsf17 contained conserved domains including a DNA binding domain, oligomerization domain, and transcriptional activation domain. The protein was nuclear localized and had transcription activation activity. Yeast two-hybrid and split luciferase complementation assays confirmed the interaction of ZmHsf17 with members of the maize HsfA2 subclass. Overexpression of ZmHsf17 in maize significantly increased chlorophyll content and net photosynthetic rate, and enhanced the stability of cellular membranes. Through integrative analysis of ChIP-seq and RNA-seq datasets, ZmPAH1, encoding phosphatidic acid phosphohydrolase of lipid metabolic pathways, was identified as a target gene of ZmHsf17. The promoter fragment of ZmPAH1 was bound by ZmHsf17 in protein-DNA interaction experiments in vivo and in vitro. Lipidomic data also indicated that the overexpression of ZmHsf17 increased levels of some critical membrane lipid components of maize leaves under heat stress. This research provides new insights into the role of the ZmHsf17-ZmPAH1 module in regulating thermotolerance in maize.

Plants host a range of DNA elements capable of self-replication. These molecules, usually associated to the activity of transposable elements or viruses, are found integrated in the genome or in the form of extrachromosomal DNA. The activity of these elements can impact genome plasticity by a variety of mechanisms, including the generation of structural variants, the shuffling of regulatory or coding DNA sequences across the genome, and DNA endoduplication. This plasticity can dynamically alter gene expression and genome stability, ultimately affecting plant development or the response to environmental changes. While the activation of these elements is often considered deleterious to the genome, their role in creating variation is important in adaptation and evolution. Moreover, the mechanisms by which mobile DNA proliferate have been exploited for plant engineering, or contributed to understand how desirable traits can be generated in crops. In this review, we discuss the origins and the roles of mobile DNA element activity on genome plasticity and plant biology, as well as their potential function and current application in plant biotechnology.

The endoplasmic reticulum (ER) is a specialized organelle that connects almost all subcellular structures from the plasma membrane to the nucleus. The ER is involved in secretory protein synthesis, folding, and processing. Evidence has emerged that the ER is at the frontier of the battle between plant hosts and pathogens. Its structural and functional homeostasis is crucial for the survival of plant cells. Pathogens secrete effectors to take over normal functions of the ER, while host plants fight back to activate ER stress responses. Exciting advances have been made in studies on host plant-pathogen dynamics during the past decades, namely some new players involved have been recently resolved from both pathogens and hosts. In this review, we summarize advances in identifying structural characteristics of the key pathways and effectors targeting the ER. Newly identified ER-phagy receptors and components downstream of inositol-requiring 1 (IRE1) will be described. Future studies will be envisaged to further our understanding of the missing parts in this dynamic frontier.

Common bacterial blight (CBB) is a devastating seed-transmitted disease of common bean (Phaseolus vulgaris L.), caused by Xanthomonas phaseoli pv. phaseoli and Xanthomonas citri pv. fuscans. The genes responsible for CBB resistance are largely unknown. Moreover, the lack of a reproducible and universal transformation protocol limits the study of genetic traits in common bean. We produced X. phaseoli pv. phaseoli strains expressing artificially designed transcription-activator like effectors (dTALEs) to target 14 candidate genes for resistance to CBB based on previous transcriptomic data. In planta assays in a susceptible common bean genotype showed that induction of PvOFP7, PvAP2-ERF71, or PvExpansinA17 expression by dTALEs resulted in CBB symptom reduction. After PvOFP7 induction, in planta bacterial growth was reduced at early colonization stages, and RNA-seq analysis revealed up-regulation of cell wall formation and primary metabolism, together with major down-regulation of heat shock proteins. Our results demonstrated that PvOFP7 contributes to CBB resistance, and underlined the usefulness of dTALEs for functional validation of genes whose induction impacts Xanthomonas-plant interactions.

Plant signaling peptides, also known as phytocytokines, play a crucial role in cell-to-cell communication during plant development and immunity. The detection of small peptides in plant tissues is challenging and often relies on time-consuming and cost-intensive approaches. Here, we present an ELISA-based assay as a rapid and cost-effective method for the detection of naturally released peptides in plant tissues. Our ELISA-based method was developed to detect Zip1, a 17-amino-acid phytocytokine derived from Zea mays that elicits salicylic acid signaling in maize leaves. Using a custom peptide-antibody, we designed an experimental pipeline to achieve peptide specificity, selectivity, and sensitivity allowing the detection of the Zip1 peptide in complex biological samples. As a proof of concept, we first overexpressed the precursor molecule PROZIP1 in Nicotiana benthamiana and in transfected maize protoplasts and monitored the release of Zip1-containing peptides. In a second approach we treated maize leaves with salicylic acid to induce native PROZIP1 expression and processing. Using ELISA, we were able to quantify native Zip1 signals with a detection limit in the nanogram range, which allowed us to detect different Zip1-containing peptides in plant material. This method can be adapted for the detection and quantification of a variety of plant signaling peptides.

Rice HRS1 HOMOLOG3 (OsHHO3) acts as a transcriptional repressor of AMMONIUM TRANSPORTER1 (OsAMT1) genes in rice; thus, reduced OsHHO3 expression in nitrogen (N)-deficient environments promotes ammonium uptake. In this study, we show that OsHHO3 also functions as a repressor of a specific subset of phosphate (Pi) transporter (PT) genes involved in the uptake and root-to-shoot translocation of Pi, including OsPT2, OsPT4, and OsPHO1;1. Disruption of OsHHO3 increased Pi uptake and Pi contents in shoots and roots, while overexpression of OsHHO3 caused the opposite effects. Furthermore, phosphorus (P) deficiency slightly decreased OsHHO3 expression, up-regulating a specific subset of PT genes. However, N deficiency was more effective than P deficiency in suppressing OsHHO3 expression in roots, and unlike N deficiency-dependent activation of PT genes under the control of OsHHO3, the P deficiency-dependent activation of OsAMT1 genes was minimal. Interestingly, the simultaneous deficiency of both N and P promoted the OsHHO3-regulated expression of PT genes more significantly than the deficiency of either N or P, but diminished the expression of genes regulated by OsPHR2, a master regulator of Pi starvation-responsive transcriptional activation. Phenotypic analysis revealed that the inactivation and overexpression of OsHHO3 improved and reduced plant growth, respectively, under N-deficient and P-deficient conditions. These results indicate that OsHHO3 regulates a specific subset of PT genes independently of OsPHR2-mediated regulation and plays a critical role in the adaptation to diverse N and P environments.

Adaptation to drought is one of the most important challenges for agriculture. The root system, and its integration with the soil, is fundamental in conferring drought tolerance. At the same time, it is extremely challenging to study. The result is that investigations aimed at increasing crop drought tolerance have mainly focused on above-ground traits, especially for perennial species. In this review, we explore the root trait syndromes that would constitute drought tolerant ideotypes, taking the example of grapevine as a model perennial grafted plant. We introduce and discuss the complexity of root trait interactions across different spatial and temporal scales considering their diversity, plasticity, and possible trade-offs. Finally, we review future approaches for discovering hidden root trait syndromes conferring drought tolerance, such as state-of-the-art root phenotyping technologies, the use of modeling as a tool to upscale root traits to the field, and new strategies to link genes to phenotypes. Together these integrated approaches can improve the breeding of drought tolerant grapevine rootstocks.

The complex gene regulatory landscape underlying early flower development in Arabidopsis has been extensively studied through transcriptome profiling, and gene networks controlling floral organ development have been derived from the analyses of genome wide binding of key transcription factors. In contrast, the dynamic nature of the proteome during the flower development process is much less understood. In this study, we characterized the floral proteome at different stages during early flower development and correlated it with unbiased transcript expression data. Shotgun proteomics and transcript profiling were conducted using an APETALA1-based floral induction system. A specific analysis pipeline to process the time-course proteomics data was developed. In total, 8,924 proteins and 23,069 transcripts were identified. Co-expression analysis revealed that RNA-protein pairs clustered in various expression pattern modules. An overall positive correlation between RNA and protein level changes was observed, but subgroups of RNA/protein pairs with anticorrelated gene expression changes were also identified and found to be enriched in hormone responsive pathways. In addition, the RNA-seq dataset reported here further expanded the identification of genes whose expression changes during early flower development, and its combination with previously published AP1 ChIP-seq datasets allowed the identification of additional AP1 direct and high-confidence targets.

DNA methylation plays a crucial role in regulating fruit ripening and seed development. It remains unknown about the dynamic characteristics of DNA methylation and its regulation mechanisms in morpho-physiological dormancy (MPD)-typed seeds with recalcitrant characteristics. The Panax notoginseng seeds are defined by the MPD and are characterized by a strong sensitivity to dehydration during the after-ripening process. We performed DNA methylomes, siRNA profiles, and transcriptomes of embryo and endosperm in P. notoginseng seeds at different after-ripening stages. Herein, we find that the hyper-methylation contributes to the increase in DNA methylation during the after-ripening process. The endosperm genome is hyper-methylated compared to the embryo genome. The hyper-methylation is caused by the high expression level of DNA methyltransferase PnCMT2 in the seeds. The hyper-methylation alters gene transcription levels to regulate the after-ripening and dormancy of recalcitrant seeds. For example, it inhibits the expression of genes in embryo development to make seeds maintain a dormant status. Together, our findings reveal an increase in DNA methylation and its vital driver in gene expression, and thus elucidate how hyper-methylation regulates the after-ripening in recalcitrant MPD-typed seeds. This work establishes a key role for epigenetics in regulating the dormancy of MPD-typed seeds with recalcitrant characteristics.