Plant Cell最新文献

In plants, embryo size is determined via interactions between metabolic and developmental signals. Maize (Zea mays) big embryo 6 (bige6) enhances embryo size while sharply reducing plant growth. Here, we show that BigE6 encodes a plastidial prephenate aminotransferase (PPA-AT), a key enzyme in the arogenate pathway for L-phenylalanine (Phe) and L-tyrosine (Tyr) biosynthesis. The maize BigE6 paralog, BigE6Like, encodes a cytosol-localized PPA-AT, revealing Phe and Tyr biosynthesis via cytosolic arogenate as a potential alternative to the known cytosolic phenylpyruvate pathway. Moreover, the single PPA-AT gene of Arabidopsis (Arabidopsis thaliana) encodes plastidial and cytosolic enzymes by alternative splicing. Transgenic rescue of a ppa-at mutant in Arabidopsis demonstrates that the plastidial PPA-AT is indispensable for seed formation due, in part, to its essential role in the female gametophyte. Leaves of bige6 maize maintained overall homeostasis for aromatic amino acids and downstream metabolites, revealing a resilience of mechanisms that scale growth to a limiting supply of Phe and Tyr. In bige6 seeds, broad perturbation of amino acid homeostasis is associated with transcriptomic upregulation of growth processes in the embryo and endosperm, implicating amino acid signaling in the regulation of embryo size. Our findings reveal the complexity and developmental dependence of growth responses to limiting amino acid biosynthesis.

PHYTOCHROME-INTERACTING FACTORs (PIFs) regulate growth-related gene expression in response to environmental conditions. Among their diverse functions in regulating signal responses, PIFs play an important role in thermomorphogenesis (the response to increased ambient temperature) and in the shade avoidance response. While numerous studies have examined the varied roles of PIFs in Arabidopsis (Arabidopsis thaliana), their roles in crop plants remain poorly investigated. This study delves into the conservation of PIFs activity among species by examining their functions in tomato (Solanum lycopersicum) and comparing them to known PIF functions in Arabidopsis using single and higher-order mutants of tomato PIF genes (SlPIFs). We demonstrate that, in contrast to Arabidopsis, PIFs are not required for thermomorphogenesis-induced stem elongation in tomato. In addition, whereas Arabidopsis PIF8 has a minor effect on plant growth, tomato SlPIF8a plays a key role in the low red/far-red (R/FR) response. In contrast, SlPIF4 and SlPIF7s play minor roles in this process. We also investigated the tissue-specific low R/FR response in tomato seedlings and demonstrate that the aboveground organs exhibit a conserved response to low R/FR, which is regulated by SlPIFs. Our findings provide insights into PIF-mediated responses in crop plants, which may guide future breeding strategies to enhance yield under high planting densities.

The significance of research conducted on Arabidopsis thaliana cannot be overstated. This focus issue showcases how insights from Arabidopsis have opened new areas of biology and directly advanced our understanding of crops. Here, experts intimately involved in bridging between Arabidopsis and crops share their perspectives on the challenges and opportunities for translation. First, we examine the translatability of genetic modules from Arabidopsis into maize, emphasizing the need to publish well-executed translational experiments, regardless of outcome. Second, we highlight the landmark success of HB4, the first GM wheat cultivar on the market, whose abiotic tolerance is borne from direct translation and based on strategies first outlined in Arabidopsis. Third, we discuss the decades-long journey to engineer oilseed crops capable of producing omega-3 fish oils, with Arabidopsis serving as a critical intermediary. Fourth, we explore how direct translation of starch synthesizing proteins characterized in Arabidopsis helped uncover novel mechanisms and functions in crops, with potential valuable applications. Finally, we illustrate how shared molecular factors between Arabidopsis and barley exhibit distinct molecular wiring as exemplified in cuticular and stomatal development. Together, these vignettes underscore the pivotal role of Arabidopsis as a foundational model plant while highlighting the challenges of translating discoveries into field-ready, commercial cultivars with enhanced knowledge-based traits.

Arabidopsis thaliana is currently the most-studied plant species on earth, with an unprecedented number of genetic, genomic, and molecular resources having been generated in this plant model. In the era of translating foundational discoveries to crops and beyond, we aimed to highlight the utility and challenges of using Arabidopsis as a reference for applied plant biology research, agricultural innovation, biotechnology, and medicine. We hope that this review will inspire the next generation of plant biologists to continue leveraging Arabidopsis as a robust and convenient experimental system to address fundamental and applied questions in biology. We aim to encourage laboratory and field scientists alike to take advantage of the vast Arabidopsis datasets, annotations, germplasm, constructs, methods, and molecular and computational tools in our pursuit to advance understanding of plant biology and help feed the world's growing population. We envision that the power of Arabidopsis-inspired biotechnologies and foundational discoveries will continue to fuel the development of resilient, high-yielding, nutritious plants for the betterment of plant and animal health and greater environmental sustainability.

Seed size and weight are pivotal agronomic traits that link plant sexual reproduction to subsequent seedling establishment. These 2 seed characteristics are affected by embryo development and sugar filling. However, the molecular mechanisms controlling sugar translocation and the timing between early embryo development and subsequent seed filling in cucumber (Cucumis sativus L.) remain poorly understood. Here, we report that alkaline α-galactosidase 2 (CsAGA2) is expressed in the placental vascular bundles and funicular phloem, and its encoded protein is responsible for the hydrolysis of raffinose family oligosaccharides (RFOs). We demonstrate that FUSCA3 (CsFUS3) activates, while Auxin Response Factor 9 (CsARF9) represses, CsAGA2 expression. The CsFUS3-Sucrose Non-fermenting-1 (Snf1)-Related Protein Kinase 1α1 (CsSnRK1α1) interaction further enhances CsAGA2 expression, while CsARF9 recruits the TOPLESS (CsTPL) corepressor and further weakens CsAGA2 expression. Transgenic CsAGA2-RNAi (RNA interference), CsFUS3-RNAi, csfus3-crispr, and CsARF9-OE (overexpression) lines showed severe seed abortion rates, likely caused by reduced sugar supply during embryo development and seed filling. These results demonstrate the critical collaborative roles of these proteins in delivering sugars for seed development. Our findings reveal that CsAGA2 is an essential enzyme that is switched on by CsFUS3 to precisely regulate embryo development and provide the vast quantities of sugars needed for seed filling in cucumber. As the seeds mature, CsARF9 dampens CsAGA2 expression to gradually reduce the sugar supply to seeds. Therefore, our data suggest that the CsFUS3 and CsARF9 sequentially regulate embryo development and seed filling via CsAGA2-mediated RFO catabolism in cucumber. Our findings provide a new strategy for manipulating seed filling to increase yield in the breeding process of seed crops.

Circular RNAs (circRNAs) are prevalent in eukaryotic cells and have been linked to disease progressions. Their unique circular structure and stability make them potential biomarkers and therapeutic targets. Compared to animal models, plant circRNA research is still in its infancy. The lack of effective tools to specifically knock down circRNAs without affecting host gene expression has slowed the progress of plant circRNA research. Here, we have developed a CRISPR-Cas13d tool that can specifically knock down circRNAs in plant systems, successfully achieving the targeted knockdown of circRNAs in rice (Oryza sativa). We further focused on Os-circANK (a circRNA derived from Ankyrin repeat-containing protein), a circRNA differentially expressed in rice upon pathogen infection. Physiological and biochemical experiments revealed that Os-circANK functions as a sponge for miR398b, suppressing the cleavage of Cu/Zn-Superoxidase Dismutase (CSD)1/CSD2/Copper Chaperone for Superoxide Dismutase (CCSD)/Superoxidase Dismutase (SODX) through ceRNA (competing endogenous RNA), leading to reduced ROS levels following Xanthomonas oryzae pv. oryzae (Xoo) infection and a negative regulation of rice resistance to bacterial blight. Our findings indicate Os-circANK inhibits rice resistance to bacterial blight via the microRNA398b(miR398b)/CSD/SOD pathway.

Some herbicide-resistant weeds become resistant by generating additional copies of specific loci. For example, amplification of the locus encoding chloroplastic glutamine synthetase (GS2) produces herbicide resistance in the glufosinate-resistant Palmer amaranth (Amaranthus palmeri) accession MSR2. Previously, overamplification of the glyphosate-resistant gene encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in Palmer amaranth was determined to be driven by an extrachromosomal circular DNA (eccDNA). Here, we describe a rearranged eccDNA that confers resistance to both glyphosate and glufosinate ammonium due to the coduplication of the native chromosomal regions that contain the genes that encode for these herbicides target proteins. In addition to EPSPS, the replicon carries 2 GS2 isoforms (GS2.1 and GS2.2) and other genes. MSR2 samples harbored eccDNA carrying only EPSPS coexisting with eccDNAs harboring both EPSPS and GS2. A second glufosinate-resistant Palmer amaranth accession (MSR1) showed distinct GS2.1 and GS2.2 amplification patterns from MSR2, suggesting the existence of diverse replicons in Palmer amaranth. EPSPS copy number was correlated with both GS2 isoforms copy number in MSR2, further supporting the coexistence of these genes in the same replicon. These findings shed light on the complexity of eccDNA formation in plant systems, with the collection and accumulation of extra pieces of DNA.

Arabidopsis thaliana (Arabidopsis) Ataxia Telangiectasia Mutated (ATM) kinase plays a vital role in orchestrating leaf senescence; however, the precise mechanisms remain elusive. Here, our study demonstrates that ATM kinase activity is essential for mitigating age- and reactive oxygen species-induced senescence, as restoration of wild-type ATM reverses premature senescence in the atm mutant, while a kinase-dead ATM variant is ineffective. ATM physically interacts with and phosphorylates Mitogen-Activated Protein Kinase Phosphatase 2 (MKP2) to enhance stability under oxidative stress. Mutations in putative phosphorylation sites S15/154 on MKP2 disrupt its phosphorylation, stability, and senescence-delaying function. Moreover, mutation of mitogen-activated protein kinase 6, a downstream target of MKP2, alleviates the premature senescence phenotype of the atm mutant. Notably, the dual-specificity protein phosphatase 19 (HsDUSP19), a predicted human counter protein of MPK2, interacts with both ATM and HsATM and extends leaf longevity in Arabidopsis when overexpressed. These findings elucidate the molecular mechanisms underlying the role of ATM in leaf senescence and suggest that the ATM-MKP2 module is likely evolutionarily conserved in regulating the aging process across eukaryotes.

Spindle assembly in vertebrates requires the Aurora kinase, which is targeted to microtubules and activated by TPX2 (Targeting Protein of XKLP2). In Arabidopsis (Arabidopsis thaliana), TPX2-LIKE 3 (TPXL3), but not the highly conserved TPX2, is essential. To test the hypothesis that TPXL3 regulates the function of α Aurora kinase in spindle assembly, we generated transgenic Arabidopsis lines expressing an artificial microRNA targeting TPXL3 mRNA (amiR-TPXL3). The resulting mutants exhibited growth retardation, which was linked to compromised TPXL3 expression. In the mutant cells, α Aurora was delocalized from spindle microtubules to the cytoplasm, and spindles were assembled without recognizable poles. A functional TPXL3-GFP fusion protein first prominently appeared on the prophase nuclear envelope. Then, TPXL3-GFP localized to spindle microtubules (primarily toward the spindle poles, like γ-tubulin), and finally to the re-forming nuclear envelope during telophase and cytokinesis. However, TPXL3 was absent from phragmoplast microtubules. In addition, we found that the TPXL3 N-terminal Aurora-binding motif, microtubule-binding domain, and importin-binding motif, but not the C-terminal segment, were required for its mitotic function. Expression of truncated TPXL3 variants enhanced the defects in spindle assembly and seedling growth of amiR-TPXL3 plants. Taken together, our findings uncovered the essential function of TPXL3, but not TPX2, in targeting and activating α Aurora kinase for spindle apparatus assembly in Arabidopsis.