Plant, Cell & Environment最新文献

Moniliophthora perniciosa is the causal agent of the witches' broom disease of cacao (Theobroma cacao), and it can infect the tomato (Solanum lycopersicum) 'Micro-Tom' (MT) cultivar. Typical symptoms of infection are stem swelling and axillary shoot outgrowth, whereas reduction in root biomass is another side effect. Using infected MT, we investigated whether impaired root growth derives from hormonal imbalance or sink competition. Intense stem swelling coincided with a reduction in root biomass, predominantly affecting lateral roots. RNA-seq analyses of root samples identified only a few differentially expressed genes involved in hormone metabolism, and root hormone levels were not expressively altered. Inoculation of the auxin highly-sensitive entire mutant genotype maintained the impaired root phenotype; in contrast, the low-cytokinin MT transgenic line overexpressing CYTOKININ OXIDASE-2 (35S::AtCKX2) with fewer symptoms did not exhibit root growth impairment. Genes involved in cell wall, carbohydrate, and amino acid metabolism were downregulated, accompanied by lower levels of carbohydrate and amino acid in roots, suggesting a reduction in metabolite availability. ¹³CO₂ was supplied to MT plants, and less ¹³C was detected in the roots of infected MT but not in those of 35S::AtCKX2 line plants, suggesting that cytokinin-mediated sugar sink establishment at the infection site may contribute to impaired root growth. Exogenous sucrose application to roots of infected MT plants partially restored root growth. We propose that the impairment of lateral root development is likely attributed to disrupted sugar signalling and photoassimilate supply by establishing a strong sugar sink at the infected stem.

Abiotic stressors, such as salt stress, can reduce crop productivity, and when combined with biotic pressures, such as insect herbivory, can exacerbate yield losses. However, salinity-induced changes to plant quality and defenses can in turn affect insect herbivores feeding on plants. This study investigates how salinity stress in tomato plants (Solanum Lycopersicum cv. Better Boy) impacts the behavior and performance of a devastating insect pest, the tomato fruitworm caterpillar (Helicoverpa zea). Through choice assays and performance experiments, we demonstrate that salt-stressed tomato plants are poor hosts for H. zea, negatively affecting caterpillar feeding preferences and growth rates. While changes in plant nutritional quality were observed, the primary factor influencing insect performance appears to be direct ionic toxicity, which significantly impairs multiple life history parameters of H. zea including survival, pupation, adult emergence, and fecundity. Plant defense responses show complex interactions between salt stress and herbivory, with two proteinase inhibitor genes - PIN2 and AspPI, showing a higher induced response to insect herbivory under salt conditions. However, plant defenses do not seem to be the main driver of reduced caterpillar performance on salt-treated plants. Furthermore, we report reduced oviposition by H. zea moths on salt-treated plants, which was correlated with altered volatile emissions. Our findings reveal that H. zea exhibits optimal host selection behaviours for both larval feeding and adult oviposition decisions, which likely contribute to its success as an agricultural pest. This research provides insights into the complex interactions between abiotic stress, plant physiology, and insect behaviour, with potential implications for pest management strategies in saline agricultural environments.

Phosphorus (P) is vital for plant growth, and continuous P fertiliser application is necessary to increase yield and quality, but it can cause environmental pollution. Plants maintain a steady phosphate (Pi) supply through complex signalling pathways. Phosphate starvation response 1 (PHR1), a key regulator of Pi starvation signals in plants, enables plants to maintain a sufficient Pi level. However, the role of PHR1 in fruit quality remains unclear. In this study, we determined the function of PHR1 in Fragaria vesca (FvPHR1) by overexpressing the FvPHR1 gene. We identified and validated two downstream genes of FvPHR1 by investigating plant phenotypes and analysing RNA-Seq data. FvPHR1 directly enhanced the expression of phosphate transporter 1;7 (FvPHT1;7), increasing Pi uptake and improving photosynthesis efficiency. Additionally, FvPHR1 upregulated the expression of sugar will eventually be exported transporter 9 (FvSWEET9), which encodes a sugar transporter that facilitates sugar transport from leaves to fruit. FvPHR1 can enhance photosynthetic products in a source via the phosphate signalling pathway and facilitate sugar transport to a sink through FvSWEET9. FvPHR1 plays a complicated role in improving fruit quality, providing a molecular foundation for developing strawberry cultivars with highly efficient Pi utilisation processes and high sugar content.

The cuticle, an extracellular hydrophobic layer impregnated with waxy lipids, serves as the primary interface between plant leaves and their environment and is thus subject to external cues. A previous study on poplar leaves revealed that environmental conditions outdoors promoted the deposition of about 10-fold more cuticular wax compared to the highly artificial climate of a growth chamber. Given that light was the most significant variable distinguishing the two locations, we hypothesized that the quantity of light might serve as a key driver of foliar wax accumulation. Thus, this study aimed to isolate the factor of light quantity (photosynthetic photon flux density [PPFD]) from other environmental stimuli (such as relative humidity and ambient temperature) and explore its impact on cuticular wax deposition and subsequent rates of residual foliar transpiration in different species. Analytical investigations revealed a significant increase in cuticular wax amount with increasing PPFD (between 50 and 1200 µmol m^-2 s^-1) in both monocotyledonous (maize and barley) and dicotyledonous (tomato and bean) crop species, without altering the relative lipid composition. Despite the increased wax coverages, rates of foliar water loss did not decrease, further confirming that the residual (cuticular) transpiration is independent of the cuticular wax amount.

The C₄ type of dicotyledonous plants exhibit a higher density of reticulate veins than the C₃ type, with a nearly 1:1 ratio of mesophyll cells (MCs) to bundle sheath cells (BSCs). To understand how this C₄-type cell pattern is formed, we identified two SCARECROW (SCR) genes in C₄ Flaveria bidentis, FbSCR1 and FbSCR2, that fully or partially complement the endodermal cell layer-defective phenotype of Arabidopsis scr mutant. We then created FbSCRs promoter β-glucuronidase reporter (GUS) lines of F. bidentis, which showed GUS expression in BSCs and their progenitor cells. The GUS expression pattern in F. bidentis transformants and comparison with the closely related C₃-type Flaveria pringlei revealed that higher-order veins were initiated in the early leaf developmental stage. Treatment with an auxin polarity transport inhibitor decreased the MC area and led to vein formation without free ends, resulting in the formation of BSCs in positions adjacent to other BSCs. However, BSC differentiation was not affected, as evidenced by BSC specific FbSCR1 expression and RuBisCO accumulation. These results indicate that polar auxin transport is important for MC proliferation and/or differentiation, which leads to the formation of a C₄-type cell pattern in which MCs and BSCs are equally adjacent.

Nitrate reduction requires reducing equivalents produced by the photosynthetic electron transport chain. Therefore, it has been suggested that nitrate assimilation provides a sink for electrons under high light conditions. We tested this hypothesis by monitoring photosynthetic efficiency and the chloroplastic glutathione redox potential (chl-E_GSH) of plant lines with mutated glutamine synthetase 2 (GS2) and ferredoxin-dependent glutamate synthase 1 (GOGAT1). Mutant lines incorporated significantly less isotopically-labelled nitrate into amino acids than wild-type plants, demonstrating impaired nitrogen assimilation. When nitrate assimilation was compromised, photosystem II (PSII) proved more vulnerable to photodamage. The effect of the nitrate assimilation pathway on the chl- E_GSH was monitored using the chloroplast-targeted roGFP2 biosensor (chl-roGFP2). Remarkably, while oxidation followed by reduction of chl-roGFP2 was detected in WT plants in response to high light, oxidation values were stable in the mutant lines, suggesting that chl-E_GSH relaxation after high light-induced oxidation is achieved by diverting excess electrons to the nitrogen assimilation pathway. Importantly, similar ΦPSII and chl-roGFP2 patterns were observed at elevated CO_2, suggesting that mutant phenotypes are not associated with photorespiration activity. Together, these findings indicate that the nitrogen assimilation pathway serves as a sustainable energy dissipation route, ensuring efficient photosynthetic activity and fine-tuning redox metabolism under light-saturated conditions.

The HKT-type proteins have been extensively studied and have been shown to play important roles in long-distance Na⁺ transport, maintaining ion homoeostasis and improving salt tolerance in plants. However, there have been no reports on the types, characteristics and functions of HKT-type proteins in Limonium bicolor, a recretohalophyte species with the typical salt gland structure. In this study, five LbHKT genes were identified in L. bicolor, all belonging to subfamily 1 (HKT1). There are many cis-acting elements related to abiotic/biotic stress response on the promoters of the LbHKT genes. LbHKT1;1 was investigated in detail. Subcellular localization results showed that LbHKT1;1 is targeted to the plasma membrane. Functional analysis in yeast showed that LbHKT1;1 has a higher tolerance than AtHKT1;1 under high Na⁺ conditions. Silencing and overexpression of the LbHKT1;1 gene in L. bicolor showed that LbHKT1;1 negatively regulates salt secretion by the salt glands. Further experiments showed that LbbZIP52 can specifically bind to the ABRE element in the LbHKT1;1 promoter and regulate the expression of the LbHKT1;1 gene and is involved in the negative regulation of the salt secretion capacity of L. bicolor. This study demonstrates for the first time that the HKT-type protein is involved in salt secretion by salt glands and provides a new perspective on the function of HKT-type proteins under salt stress conditions.

Growth heterosis is crucial for Populus deltoides breeding, a key industrial-timber and ecological-construction tree species in temperate regions. However, the molecular mechanisms underlying carbon (C)-nitrogen (N) metabolism coordination in regulating growth heterosis remain unclear. Herein high-hybrids of P. deltoides exhibited high-parent heterosis and mid-parent heterosis in growth traits and key enzymes of C-N metabolism. In hybrids, gene expression patterns were mainly biased toward female parent. Parental contribution to growth heterosis in P. deltoides is differentiation, rather than absolute maternal or paternal dominance contributions. Parental genes were predominantly and dynamically inherited in a non-additive manner, mainly with dominant expression patterns. A total of 44 non-additive genes associated with photosynthetic C fixation, starch and sucrose metabolism, sucrose transport, photorespiration, and nitrogen metabolism coregulated growth heterosis by coordinating C-N metabolism. Growth-regulating factors 4 interacted with DELLA genes to promote growth by enhancing this coordination. Additionally, five critical genes were identified. Briefly, the above genes in high-hybrids improved photosynthesis and N utilisation by regulating carbohydrate accumulation and enzyme activity, while reducing respiratory energy consumption, thereby providing more energy for growth and promoting growth heterosis. Our findings offer new insights and theoretical basis for deep understanding genetic and molecular regulation mechanisms of tree heterosis and its application in precision hybrid breeding.

In acidic soil conditions, aluminium (Al) limits crop growth and yields but benefits the growth of tea plants. Flavonols are suggested to form complexes with Al, enhancing Al accumulation in tea plants. The role of flavonols in promoting lateral root formation under Al stress remains unclear. Here, we identified a 7-rhamnosylated type of flavonol glycosides (F2-type) crucial for this process in tea roots. Al treatment significantly stimulated lateral root initiation and bud germination in tea plants, enhancing flavonol glycoside accumulation, particularly the F2-type. Most genes in the flavonol biosynthetic pathway were upregulated post-Al treatment, including CsUGT89AC2/3 genes, which catalyze F2-type flavonol glycosides synthesis in vitro and in vivo. Overexpression of CsUGT89AC2/3 increased lateral root occurrence, flavonol glycoside accumulation and expression of biosynthetic pathway genes in tea roots. Kaempferol treatment activated flavonol pathway genes and stimulated lateral root growth. Al treatment, kaempferol treatment and CsUGT89AC3 overexpression accelerated auxin accumulation and expression of auxin-related genes. Therefore, Al stimulates flavonol biosynthetic pathway gene expression, regulates F2-type flavonol biosynthesis, and influences auxin homoeostasis, promoting lateral root formation in tea plants. These findings lay the foundation for further investigation into the mechanisms underlying the Al-mediated promotion of lateral root initiation in tea plants.

Lactate dehydrogenase plays a key role in alleviating hypoxia during prolonged submergence. To explore the function of the OsLdh7 gene in enhancing submergence tolerance, we overexpressed this gene in rice (Oryza sativa cv. IR64) and subjected the transgenic lines to complete inundation. The overexpression lines showed enhanced viability, chlorophyll content and photosystem II (PSII) efficiency compared to wild-type (WT) plants under stress and recovery conditions. Additionally, these lines exhibited better starch accumulation and reduced reactive oxygen species (ROS) accumulation. Protein-protein interaction studies revealed that OsLdh7 interacts with OsLos2, OsPdc2, OsAlaAT2 and OsAsp2. Under submergence, enhanced enzyme activities of OsLdh7, OsAsp2 and OsAdh1 led to higher NAD⁺ levels, sustaining anaerobic glycolytic flux and increasing pyruvate, a critical carbon source for amino acid metabolism as well as anaerobic fermentation pathways. Elevated l-lactate levels resulted in increased activity of OsPdc2, which eventually led to enhanced ethanol production. The overexpression lines also accumulated higher levels of aspartate, glutamate and alanine, crucial for ROS reduction and energy production during recovery. These findings suggest that OsLdh7 overexpression confers tolerance to submergence stress by regulating the important metabolic pathways- anaerobic glycolysis, ethanolic fermentation and amino acid metabolism in rice.