The efficient colonization of plant-beneficial Pseudomonas spp. is a prerequisite for their biocontrol capacity.  Prior work revealed that the PcoI/PcoR quorum-sensing (QS) system plays a pivotal role in the root colonization of P. fluorescens 2P24.  During the colonization, strain 2P24 has faced diverse impacts from plant-derived reactive oxygen species and other environmental stress.  However, the molecular mechanism by which the PcoI/PcoR QS system is regulated under unfavored conditions remains unclear.  Thus, in this study, the role of the (p)ppGpp synthetase RelA and the bifunctional (p)ppGpp synthase/hydrolase SpoT in the PcoI/PcoR QS system of P. fluorescens was investigated.  Our data indicated that the deficiency of relA and spoT genes remarkably improved the expression of the pcoI gene, whereas the mutation of the spoT gene significantly repressed the expression of the pcoI gene.  We further demonstrated that the regulation of the PcoI/PcoR QS system by (p)ppGpp was dependent on the function of the trmE gene, which encodes a tRNA modification GTPase.  Furthermore, the mutation of relA, spoT, or both significantly influenced the motility, biofilm formation, oxidative stress, osmotic tolerance, and rhizosphere colonization.  Collectively, our data indicated that the (p)ppGpp signaling pathway mediated by the relA gene and spoT gene was important to the function of the PcoI/PcoR QS system and had important implications for the understanding of the molecular mechanism of (p)ppGpp in epiphytic fitness via TrmE of P. fluorescens.

Introducing the inherent genetic diversity of wild species into cultivars has become one of the hot topics in crop genetic breeding and genetic resource research.  Fiber- and seed-related traits, which are critical to the global economy and people’s livelihoods, are the principal focus of cotton breeding.  Here, the wild cotton species Gossypium tomentosum was used to broaden the genetic basis of G. hirsutum and identify QTLs for fiber- and seed-related traits.  A population of 559 chromosome segment substitution lines (CSSLs) was established with various chromosome segments from G. tomentosum in a G. hirsutum cultivar background.  Totals of 72, 89, and 76 QTLs were identified for three yield traits, five fiber quality traits, and six cottonseed nutrient quality traits, respectively.  Favorable alleles of 104 QTLs were contributed by G. tomentosum.  Sixty-four QTLs were identified in two or more environments, and candidate genes for three of them were further identified.  The results of this study contribute to further studies on the genetic basis of the morphogenesis of these economic traits, and indicate the great breeding potential of G. tomentosum for improving the fiber- and seed-related traits in G. hirsutum.

Invasive alien species (IAS) are a major driver of biodiversity loss, which poses substantial threats to food security, ecological integrity, and public health. Their proliferation results from synergistic interactions among species-specific traits (e.g., high reproductive capacity, and adaptability), environmental conditions, anthropogenic activities like global trade, biotic relationships, and policy frameworks. While much research has examined individual invasion drivers, emerging evidence confirms that invasion success primarily results from complex, multifactorial synergies. This review elucidates how the coupling of environmental stressors, biotic interactions, and human-mediated processes (notably habitat modification and dispersal mechanisms) accelerates the global spread of high-impact IAS, exemplified by species of global concern including Cydia pomonella, Tuta absoluta, Leptinotarsa decemlineata, Erwinia amylovora, and tomato brown rugose fruit virus (ToBRFV). We systematically evaluate how cascading interactions among these factors amplify ecological imbalances and invasion risks. Furthermore, advances in population genomics further enable critical insights into the adaptive evolution and genetic determinants of invasion success. Therefore, integrating multifactorial frameworks with genomic methodologies is vital for predicting invasion trajectories and developing targeted management strategies, underscoring the imperative for interdisciplinary approaches to mitigate the escalating threat of biological invasions.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), severely threatens the kiwifruit industry. The type III secretion system (T3SS) is a key virulence factor in Psa, but the regulatory mechanisms remain poorly understood. Polymyxin B1, the main component of polymyxin B, inhibits T3SS gene expression in Psa, yet its underlying mechanism is unclear. Cyclic diguanosine monophosphate (c-di-GMP), a crucial bacterial second messenger, is synthesized by diguanylate cyclases (DGCs) containing a GGDEF domain. In this study, we identified and characterized PSA_1379 (WspR), a GGDEF domain-containing protein in Psa. Biochemical assays demonstrated that WspR exhibits DGC activity. Virulence assays showed that WspR negatively regulates Psa virulence. RT-qPCR analyses revealed that polymyxin B induces wspR expression. Additionally, polymyxin B upregulates intracellular c-di-GMP levels and inhibits the expression of T3SS genes through WspR. Bacterial two-hybrid and GST pull-down assays confirmed that WspR interacts with the transcription factor PsrA. Both WspR and c-di-GMP inhibit the binding of PsrA to the promoter of the T3SS master regulator hrpL, thereby suppressing PsrA-mediated transcriptional activation of hrpL and ultimately repressing T3SS gene expression. This study provides new insights into Psa virulence regulation and suggests potential targets for KBC control through the WspR-c-di-GMP pathway.