Plant, Cell & Environment最新文献

Diplodia sapinea causes Diplodia tip blight (DTB) and is recognised as an opportunistic necrotrophic pathogen affecting conifers. While DTB is associated with abiotic stress, the impact of biotic stress in the host on D. sapinea's lifestyle shift is unknown. Observed co-occurrences of D. sapinea and Melampsora pinitorqua, causing pine twisting rust on Scots pine (Pinus sylvestris), instigated an investigation into their interaction with and influence on the defence mechanisms of the host. We hypothesised that M. pinitorqua infections predispose the trees to D. sapinea by stressing the host and altering the shoot metabolites. Pines in a plantation were sampled over time to study pathogen biomass and host metabolites. Symptoms of both pathogens were consistent over years, and the preceding season's symptoms affected the metabolic profiles pre-infection and M. pinitorqua's proliferation. Symptoms of M. pinitorqua altered shoot metabolites more than fungal biomass, with co-symptomatic trees exhibiting elevated M. pinitorqua biomass. Specific phenolic compounds had a strong positive association with the shoot symptom × D. sapinea interaction. D. sapinea's biomass presymptoms was independent of previous disease symptoms and infection by M. pinitorqua. Some trees showed disease tolerance, with delayed rust infections and minimal DTB symptoms. Further investigations on this trait are needed.

Heterotrophic microbes rely on host-derived carbon sources for their growth and survival. Depriving pathogens of plant carbon is therefore a promising strategy for protecting plants from disease and reducing yield losses. Importantly, this carbon starvation-mediated resistance is expected to be more broad-spectrum and durable than race-specific R-gene-mediated resistance. Although sugars are well characterized as major carbon sources for bacteria, emerging evidence suggests that plant-derived lipids are likely to be an essential carbon source for some fungal microbes, particularly biotrophs. Here, we comprehensively discuss the dual roles of carbon sources (mainly sugars and lipids) and their transport processes in immune signalling and microbial nutrition. We summarize recent findings revealing the crucial roles of lipids as susceptibility factors at all stages of pathogen infection. In particular, we discuss the potential pathways by which lipids and other plant carbon sources are delivered to biotrophs, including protein-mediated transport, vesicle trafficking and autophagy. Finally, we highlight knowledge gaps and offer suggestions for clarifying the mechanisms that underlie nutrient uptake by biotrophs, providing guidance for future research on the application of carbon starvation-mediated resistance.

The sucrose yield in sugarcane largely depends on stem morphology, including length, diameter and sugar content, making sugarcane stem a key trait in breeding. The "Bainianzhe" variety from Songxi County, Fujian Province, possesses both aerial stems and rhizomes, providing a unique model for studying stem development. We performed a spatiotemporal transcriptomic analysis of the base, middle and apical sections of both aerial stems and rhizomes. The analysis categorized transcriptomes by developmental stage-base, middle and apical-rather than environmental differences. Apical segments were enriched with genes related to cell proliferation, while base segments were linked to senescence and fibrosis. Gene regulatory networks revealed key TFs involved in stem development. Orphan genes may be involved in rhizome development through coexpression networks. Plant hormones, especially genes involved in ABA and GAs synthesis, were highly expressed in rhizomes. Thiamine-related genes were also more prevalent in rhizomes. Furthermore, the apical segments of rhizomes enriched in photosynthesis-related genes suggest adaptations to light exposure. Low average temperatures in Songxi have led to unique cold acclimation in Bainianzhe, with rhizomes showing higher expression of genes linked to unsaturated fatty acid synthesis and cold-responsive calcium signalling. This indicates that rhizomes may have enhanced cold tolerance, aiding in the plant's overwintering success.

Pollen development and germination are critical for successful generation of offspring in plants, yet they are highly susceptible to heat stress (HS). However, the molecular mechanism underlying this process has not been fully elucidated. In this study, we highlight the essential roles of two mRNA capping enzymes, named Arabidopsis mRNA capping phosphatase (ARCP) 1 and 2, in regulating male and female gamete development. The transmission efficiencies of gametes carrying arcp1 arcp2 from arcp1^+/- arcp2^-/- and arcp1^-/- arcp2^+/- mutants are 30% and zero, respectively. These mutants exhibited a significant increase in misshaped pollen, with germination rates approximately half of those in wild type. ARCP1/2 exhibit RNA triphosphatase and RNA guanylyltransferase activities, which are required for proper pollen development. Through RNA-seq analysis, genes involved in pollen development/germination and HS response were identified as downregulated genes in pollen from arcp1^+/- arcp2^-/- mutant. Furthermore, ARCP2 protein is degraded under HS condition, and inducing the expression of ARCP2 can increase the pollen germination rate under elevated temperature. We propose that HS triggers the degradation of mRNA capping enzymes, which in turn disrupts the transcriptome that required for pollen development and pollen germination and ultimately leads to male sterility.

Salt stress is the main factor limiting the large-scale cultivation of Shanxin poplar; therefore, improving its salt tolerance is crucial. In this study, we identified and characterized a CRF gene (PdbCRF5) in Shanxin poplar. Compared with the wild-type poplar, the Shanxin poplar overexpressing PdbCRF5 were more sensitive to salt stress. The PdbCRF5-silenced plants exhibited improved salt tolerance. ChIP‒PCR, EMSA, and Y1H confirmed that PdbCRF5 can regulate the expression of the PdbbZIP61 by binding to ABRE element. Further analysis revealed that the overexpression of PdbbZIP61 can reduce cell damage by increasing ROS scavenging, and on the other hand, overexpression of PdbbZIP61 can improve the salt tolerance of Shanxin poplar by regulating the expression of the PdbNCED genes to increase the ABA content. In addition, we also demonstrated that PdbCRF5 can inhibit the expression of the PdbbZIP61 in combination with PdbCRF6. The overexpression of PdbCRF6 also reduced the salt tolerance of Shanxin poplar. Therefore, we found that PdbCRF5 negatively regulates the salt tolerance of Shanxin poplar by inhibiting the PdbbZIP61, indicating that PdbCRF5 plays an important role in the tolerance of Shanxin poplar to salt stress and is an important candidate gene for gene editing and breeding in forest trees.

Fusarium oxysporum, an important soilborne fungal pathogen that causes serious Fusarium wilt disease, secretes diverse effectors during the infection. In this study, we identified a novel secreted cysteine-rich protein, FolSCP1, which contains unknown protein functional domain. Here, we characterized FolSCP1 as a secreted virulence factor that promotes the pathogen infection of host plants by inhibiting diverse plant defence responses. FolSCP1 interacted with the pathogenesis-related 5 (PR-5) protein SlPR5, a positive regulator of tomato plant immunity against multiple tomato pathogens, and effectively attenuated the antifungal activity of the tomato PR-5 protein. FoSCP1, a homologue of FolSCP1, was secreted by a F. oxysporum isolate from infected tobacco and targeted the tobacco PR-5 protein NtPR5 to suppress plant defence for further infection. In summary, our study revealed a fungal virulence strategy in which F. oxysporum secrete effectors that interfere with plant immunity by binding to the PR-5 protein of the host plant and inhibiting its biological activity, thereby promoting fungal infection.

Calmodulin, a highly conserved calcium-binding protein, plays a crucial role in response to salt stress. Previous studies investigated sequence and function of calmodulin members in some plants, but their roles in rice have not been fully elucidated. Three OsCaM1 genes namely OsCaM1-1/2/3 encode the same OsCaM1 protein. Here, we found that OsCaM1-1 had significantly higher expression than the other two genes under salt stress. After 4 weeks of exposure to 75 mM NaCl, OsCaM1-1 overexpressed mutants showed higher salt tolerance, while knocked-out mutants exhibited lower salt tolerance, compared to the wild type. Moreover, the oscam1-1 mutants had higher Na⁺ concentration and Na⁺/K⁺ ratio in both shoots and roots, less instantaneous K⁺ and Ca²⁺ fluxes in roots, compared to wild type under salt stress, indicating the involvement of OsCaM1-1 in regulation of Na⁺ and K⁺ homoeostasis via Ca²⁺ signal. RNA-seq analysis identified 452 differentially expressed genes (DEGs) regulated by OsCaM1-1 and salt stress, and they were mainly enriched in nucleus DNA-binding activities, including ABI5, WRKY76, WRKY48 and bHLH120 transcription factors. Knockout of OsCaM1-1 also modulated the expression of Na⁺ transporters, including HKT1;1, HKT1;5, SOS1, NHX1 and NHX4. In conclusion, OsCaM1-1 positively regulates salt tolerance in rice through mediating ion homoeostasis.

Chili anthracnose, a fungal disease caused by Colletotrichum scovillei, is among the most devastating diseases affecting pepper (Capsicum annuum L.). Although WRKY transcription factors play important roles in plant immunity, it is unknown how WRKY gene family members contribute to pepper plant resistance to C. scovillei. Here, CaWRKY20 was found to negatively regulate pepper resistance to C. scovillei, which was demonstrated by virus-induced gene silencing and transient overexpression in pepper. Moreover, overexpression of CaWRKY20 enhanced susceptibility to C. scovillei in tomato. Additionally, our findings demonstrated that CaWRKY20 can indirectly regulate the expression of salicylic acid (SA)-related defense genes (CaPR1, CaPR10 and CaSAR8.2) as well as reactive oxygen species (ROS)-scavenging enzyme genes (CaCAT, CaPOD and CaSOD) in response to C. scovillei. In addition, CaWRKY20 was found to interact with CaMIEL1 in the nucleus to regulate the defense response to C. scovillei in pepper. Furthermore, CaWRKY20 directly bound to the W-box in the promoter of SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (CaSARD1) and suppressed its expression, resulting in reduced resistance to C. scovillei. These results will clarify the mechanism by which WRKY transcription factors are involved in pepper disease resistance and can thus facilitate molecular breeding for anthracnose-resistant varieties.

Clonal perennial grasses are the dominant species in almost all natural grasslands, however their seed production is typically low. The reasons why seed set is so low remains unclear. We studied a rhizomatous grass (Leymus chinensis) using ¹³C tracing the different photosynthetic organs to investigate carbon fixation and allocation during the seed-filling stage. We found that the vegetative ramet leaves are the largest (81%) source for total plant fixed carbon, whereas almost all carbon is allocated to vegetative reproduction. The spike is the largest (54%) carbon source for the seeds. However, the spike produced carbon only allocated 37% to the seeds, with the majority allocated to vegetative reproduction. This preferential carbon allocation to vegetative reproduction limits sexual reproduction. Nitrogen application significantly increased assimilated carbon. However, nearly all increased carbon accumulated in the vegetative reproduction rather than in the seeds. Only the carbon produced by the spike increased its allocation to the seeds by 13%. Taken together, we conclude that the predominance of vegetative reproduction, combined with self-incompatibility, results in low ovule fertilization and very weak seed sink strength for carbon competition, suggests that the weak seed sink strength is the key reason causing low seed set in L. chinensis.