Physiologia plantarum最新文献

Organ size is regulated by multiple genes and hormonal pathways through cell number and size. Karrikins (KARs) are smoke-derived chemicals and presumed to mimic an unknown endogenous hormone, whose signaling functions in the regulation of plant growth and development. Here, we found that the KAR receptor KAR INSENSITIVE 2 (KAI2)-deficient kai2 mutant plants were larger than wild-type (WT) plants in terms of rosette leaves, siliques, petals, and seeds. Consistently, the KAR signaling negative regulator-deficient mutant plants, suppressor of max2-1 (smax1, s1) and smax1-like 2 (smxl2, s2) double mutant (s1 s2) plants, showed smaller sizes of the above-mentioned organs than WT. In pairwise comparisons, 'kai2 s1 versus WT' and 'kai2 s2 versus kai2', all these genotypes displayed comparable sizes of these organs. Detailed investigations of cell size indicated that kai2 plants have larger cells than WT plants with respect to leaf mesophyll and seed coat, while s1 s2 plants have smaller cells. Comparative transcriptome analyses of 'kai2 versus WT', 'max2 versus WT', and 's1 s2 versus WT' using rosette leaves indicated that several pathways related to organ size and hormones, including abscisic acid, auxin, cytokinins, and jasmonic acid, are regulated by KAR signaling. These results suggest that KAR signaling inhibits organ size by restricting cell expansion with the involvement of genes involved in various hormone signaling pathways and organ size determination.

Fine root respiration drives root growth and resource acquisition in cold, nutrient-poor ecosystems, yet its association with root phenology remains unclear. Non-structural carbohydrates (NSC), stored as soluble sugars and starch are primary metabolites that play key roles in physiological functions. Analyzing NSC pools and availability contributes to the understanding of the seasonality of root respiration. Here, we examined seasonal variations in fine-root respiration, sugars and starch for Abies mariesii and Betula ermanii, from spring to autumn at 2000 and 2500 m in subalpine forests. Additionally, specific root length and root nitrogen concentrations were evaluated. Root respiration rates became higher, mostly following soil temperature. Sugar concentrations were the highest in spring and the lowest in summer. In autumn, sugar accumulated earlier in the fine roots of A. mariesii than in B. ermanii. Starch concentrations and the root functional traits did not show significant seasonal variations. Significant relationships between root respiration and sugars were found in spring for B. ermanii and in autumn for A. mariesii. Furthermore, root respiration and sugars were correlated positively at 2000 m and negatively at 2500 m for both species. These differences explain that B. ermanii actively consumes stored sugars for root respiration to facilitate root elongation and resource acquisition associated with spring foliation, particularly in a shorter growing season. In contrast, A. mariesii suppresses sugar consumption via root respiration because improving cold tolerance before dormancy is critical for survival at the treeline. Therefore, NSCs play different roles in the seasonality of fine roots and determine the species-specific patterns of temperature-independent root respiration.

Autumn phenology traits are likely to be essential for the adaptation of apple to boreal climate. However, the genetic control of these traits is not well understood, and, for example, growth cessation does not appear to be controlled by day length as in many other boreal tree species. Here, I combine a quantitative genetic and population genomic approach to study autumn senescence in apple. I phenotyped a diverse germplasm collection for the timing of autumn senescence, performed quantitative trait loci (QTL) mapping in a multiparental population (MPP), and investigated genomic signals of selection to identify candidate genes. The timing of 50% autumn senescence was negatively correlated with adaptation to higher (boreal) climate zones. Two QTL were found to control the timing of autumn senescence in the MPP, exhibiting both dominance and epistatic interactions. The QTL on linkage group (LG) 17 was also variable in the diversity germplasm, while the QTL on LG11 was not. Cultivars adapted to boreal climate showed weak signals of selection at two loci within the genomic region of chromosome 17 corresponding to the LG17 QTL interval, consistent with a recent expansion to northern Sweden. These loci coincide with two predicted UGT85 genes and a possible copy number variation in PHYC, respectively. Thus, this study provides valuable information for further research and breeding of apple in light of the ongoing climate change.

Lignin is a plant cell wall phenolic polymer and the largest renewable source of aromatic carbon in nature. While lignin is essential for plant survival, little work has been carried out to understand its variation across plant tissues and developmental stages. Here, we combined microscopy, spectrophotometry, and mass spectrometry to compare lignin deposition in roots, stems, and leaves of the model plants Arabidopsis thaliana and Brachypodium distachyon across four developmental stages. Brachypodium accumulated more lignin and exhibited higher syringyl-to-guaiacyl (S/G) ratios than Arabidopsis in all stages and tissues. Lignin deposition increased across all tissues over development and was maintained during senescence, with stems and roots showing the largest lignin content and leaves contributing more substantially at senescence. Furthermore, lignification began with the deposition of G-units, followed by the accumulation of S-units, which became more predominant at later developmental stages in all tissues. Brachypodium contained more p-hydroxyphenyl (H) lignin than Arabidopsis, with the highest levels observed in roots compared to stems and leaves. Interestingly, while the S/G ratio in stems plateaued at maturity (R3 stage), roots of both species continued accumulating S-lignin during senescence (S4 stage). These results show that herbaceous monocots and dicots have different content and chemical compositions of lignin depending on the time of harvest, with implications for both biomass utilization and biological carbon sequestration.

Anthocyanin coloration of fruit, foliage, and flowers is dependent both on pigment synthesis and degradation. Our previous comprehensive study on in planta anthocyanin degradation was conducted on the purple Brunfelsia calycina flowers, whitening due to a one-step process, involving a single vacuolar peroxidase. Here, we reveal a novel two-step in planta degradation process in the purple Solanum macranthum flowers, as they whiten. This process involves both vacuolar β-glucosidases and peroxidases, similar to the in vitro processes described in fruit juices, with β-glucosidase enzymes stripping the pigments from their sugar moieties, followed by enzymes oxidizing the aglycones. We show that the activities of both β-glucosidase and peroxidase are crucial for the in planta degradation to occur in S. macranthum flowers. A specific vacuolar β-glucosidase (SmBGL7) and two peroxidase isozymes (SmPrx01, SmPrx02) increased in their activity parallel to the degradation process. One vacuolar β-glucosidase gene and two peroxidase genes are induced in the flower tissue just prior to the onset of anthocyanin degradation, with MWs related to those found for the corresponding isozymes of all three enzymes. SmPrx01 has an identical active site proximal heme-ligand signature sequence to the B. calycina degrading peroxidase gene, BcPrx01, and binds both malvidin (the main aglycone in B. calycina) and petunidin (the main aglycone in S. macranthum) equally. The second peroxidase, unique to S. macranthum, SmPrx02, has a stronger binding to petunidin than to malvidin, suggesting potential variability and synergistic involvement of peroxidases in anthocyanin degradation.

Long non-coding RNAs (lncRNAs) play an important role in plant growth and development, and they also respond to various abiotic stresses by participating in transcriptional, post-transcriptional, and epigenetic regulation. In this study, we identified salt-responsive lncRNAs in the roots and leaves of Tamarix hispida and characterized their functions. In total, 7198 mRNAs and 1112 salt-induced lncRNAs were identified using RNA-seq. The potential target genes of these salt-responsive lncRNAs were enriched in "metabolic process," "cellular process," "single-organism process," and "response to stimulus" in both roots and leaves. We identified and characterized five lncRNAs associated with salt tolerance in T. hispida (designated ThSAIR1-ThSAIR5). The expression of these lncRNAs was induced by salt stress. ThSAIR1-ThSAIR5 overexpression vectors were constructed, and overexpression plants were generated using Agrobacterium-mediated efficient transient transformation technology. The impact of elevated gene function on salt stress tolerance was then studied. The transient overexpression of ThSAIR1-ThSAIR5 enhances reactive oxygen species (ROS) scavenging capability and proline biosynthesis in T. hispida under salt stress. Additionally, the target gene of ThSAIR5, ThNAC86, was further identified through transcriptome sequencing and subsequently transformed into Arabidopsis thaliana, resulting in improved salt tolerance in the transgenic plants. These results demonstrated that ThSAIR5 positively regulates salt tolerance by modulating the expression of ThNAC86, suggesting that it may serve as a candidate gene for molecular breeding aimed at developing plants with enhanced salt tolerance.

Exogenous γ-aminobutyric acid (GABA) alleviates nitrogen (N) deficiency stress in plants; however, its effects on secondary metabolite biosynthesis in medicinal plants under such conditions remain poorly understood. This study investigated the effects of GABA on the growth and andrographolide biosynthesis in Andrographis paniculata (Chuanxinlian) under low N (LN, 1 mmol L^-1 NO₃ ^-) using soilless culture. Our findings indicated that both 5 mmol L^-1 GABA and nitrate-N (NN) treatments enhanced plant N accumulation, upregulated photosynthesis and N metabolism, and downregulated secondary metabolism such as flavonoid and andrographolide biosynthesis, consistent with the protein competition model (PCM) and carbon/nutrient balance hypothesis (CNBH). Nevertheless, compared to NN, GABA attenuated the decline in andrographolide content and maintained levels of 14-deoxyandrographolide and dehydroandrographolide. Consequently, GABA preserved the yield of diterpenoid lactones, whereas NN treatment resulted in a significant reduction. Metabolomic analyses revealed similarities between GABA-treated and control plants in glycolysis and the tricarboxylic acid (TCA) cycle. Additionally, transcriptome analysis revealed that upregulated differentially expressed genes (DEGs) in both control and GABA treatments were enriched in sulfur-related metabolism, extracellular signaling pathways, and cyanoamino acid metabolism, suggesting these processes are closely associated with the regulation of andrographolide biosynthesis. The cytochrome P450 enzymes CYP71D11 and CYP76T24 were identified as promising candidates involved in andrographolide biosynthesis. Collectively, these results demonstrate that exogenous GABA not only alleviates N deficiency stress but also mitigates reductions in andrographolide content in Chuanxinlian, suggesting that GABA presents a promising alternative to nitrate fertilizers for achieving high-yield and high-quality production of Chuanxinlian under N-deficient conditions.

As a member of the sucrose transporter (SUT) family, AtSUT4 occupies a distinct evolutionary category, implying unique functional specialization. However, studies on its involvement in growth and development regulation remain limited. Here, we demonstrated that AtSUT4 overexpression significantly inhibited root growth in Arabidopsis thaliana. Analyses using bromocresol purple indicators and non-invasive micro-test technology (NMT) revealed that AtSUT4 overexpression induced proton influx in the root apical meristem and elongation zones, while suppressing AHA1/AHA2 expression, ultimately resulting in an increased proton influx and extracellular alkalization of root tissues. Treatment with the H⁺-ATPase activator fusicoccin (FC) and the inhibitor N, N'-dicyclohexylcarbodiimide (DCCD) indicated that AHA negatively regulated AtPIN2 expression. Consequently, overexpression of AtSUT4 down-regulated AHA expression while promoting AtPIN2 expression and auxin accumulation in the root tips. Transcriptomic profiling further linked disrupted proton homeostasis and auxin accumulation to mark the down-regulation of genes encoding ribosomal proteins, tubulins, and pectin degradation enzymes. These findings suggested that AtSUT4-induced rhizosphere pH shifts and auxin perturbations concurrently impaired expansion forces (via cytoskeletal proteins) and enhanced limiting forces (via cell wall rigidity). Herein, we tentatively propose that AtSUT4 overexpression induced proton influx, which concurrently suppressed AHA1/2 expression and enhanced AtPIN2 transcription. This cascade culminated in rhizosphere alkalinization and variation of auxin distribution, collectively disrupting root cell growth. Our findings potentially established a previously unrecognized regulatory nexus between sugar signaling and auxin-mediated developmental pathways in Arabidopsis thaliana.

Quinoa is a facultative halophyte capable of thriving in harsh environmental conditions. Its epidermal bladder cells (EBCs) have been suggested to play a key role in salinity tolerance. To clarify their importance, several experiments have been conducted to assess the effects of EBC removal. However, existing studies have yielded conflicting evidence, both supporting and rejecting their significance. Notably, most of these investigations have focused on leaf EBCs, despite the fact that quinoa accumulates more ions in the stem than in the leaves. To address this gap, we designed a manipulative experiment to remove EBCs from the leaves and stems. Our results demonstrate that stem EBCs is crucial under both saline and non-saline conditions. Their removal led to reduced growth and transpiration in non-saline environments and decreased shoot biomass and Na⁺ accumulation in the shoot under saline conditions, while the removal of leaf EBCs did not alter the growth under either non-saline or saline conditions. Based on these findings, we hypothesize that stem EBCs play a role in ion homeostasis and water movement.

Soil and irrigation salinity continue to have a major impact on the world's agriculture and horticulture, and loss of plant production is likely to worsen with global warming and climate change. Efforts to mitigate salinity stress and breed better salt-tolerant plants rely on our knowledge of plant response to abiotic stress at the physiological and molecular levels. Salinity usually leads to the accumulation of free and conjugated polyamines (PAs) in plant tissues. Putrescine (Put), and its derivatives spermine (Spm) and spermidine (Spd), perform critical functions by activating biochemical, physiological and molecular defense systems, thus reducing damage caused by salinity stress. Promoting endogenous levels of PAs can improve the salt tolerance of plants. Furthermore, the application of exogenous PAs has been shown to effectively mitigate salt stress across a range of commercially important plant species. This review critically examines the biosynthesis of PAs and their associated physiological, phytochemical, and molecular responses in plants under saline conditions. In addition, it evaluates the potential of PAs as a strategic tool for enhancing salinity tolerance. The review also highlights key gaps in current knowledge and proposes directions for future research to optimize the use of PAs in salinity stress management.