Horticulturae

Lisianthus [Eustoma grandiflorum (Raf.) Shinners] is among the 10 most produced and marketed cut flowers in the world. However, its slow growth represents a challenge for its production. This study evaluated the efficiency of rhizobacterial strains in vegetative growth and nutrient acquisition in lisianthus plants. Freshly germinated seeds of lisianthus cv. Mariachi Blue Double were used. Seven rhizobacterial strains and two controls (sterile distilled water and nutrient broth) were evaluated in a completely randomized design. Replication varied among treatments and variables: shoot growth traits were assessed on 10–12 plants per treatment, root biomass on a destructive subsample of six plants per treatment and shoot nutrient contents on four composite samples per treatment. Measurements taken 149 days after sowing showed that plants inoculated with the strains Acinetobacter vivianii C48, Achromobacter xylosoxidans C56, and Arthrobacter pokkalii JLB4 had greater height, leaf area, leaf number, and fresh and dry biomass, both aerial and in the root. These strains also enhanced N and P uptake in shoot tissues. In contrast, the Bacillus pumilus strain R44 significantly decreased height and leaf number. The results suggest that strains C48, C56 and JLB4 can stimulate nutrition, accelerate plant growth, and shorten the vegetative phase in lisianthus.

Pyruvate decarboxylase (PDC) is an intracellular non-oxidizing enzyme that relies on thiamine pyrophosphate (TPP), which is important for plant survival under anaerobic conditions and increasingly recognized for its role in broader stress reaction. However, the PDC gene family of tomato (Solanum lycopersicum), an important waterlogging-sensitive agricultural product, has not yet been discovered. In this study, eight SlPDC genes were discovered within the tomato genome. Gene structure analysis revealed that SlPDC members exhibited varying intron–exon configurations, with SlPDC8 possessing the most complex structure containing seven introns. Promoter analysis revealed a multitude of cis-acting elements responsive to light, hormones, and various stresses. Particularly, the promoter of SlPDC8 contains both ABRE and TGACG/CGTCA-motif. Tissue-specific expression profiles showed that SlPDC8 was mainly highly expressed in the roots. Expression profiling demonstrated that SlPDC genes respond divergently to different abiotic stresses, including salt, hydrogen peroxide (H₂O₂), drought, waterlogging, cold, heat, darkness, and UV radiation stresses. Notably, SlPDC1, SlPDC7, and SlPDC8 were significantly upregulated by waterlogging, with SlPDC8 showing the most robust induction. Functional validation through VIGS proved that SlPDC8-silenced plants exhibited significantly impaired growth, decreased photosynthetic pigment content, severe leaf wilting, and poor root development under waterlogging conditions compared to control plants. Furthermore, silencing SlPDC8 led to increased malondialdehyde (MDA) levels and decreased antioxidant enzyme activities, indicating heightened oxidative damage under waterlogging stress. We conclusively demonstrate that SlPDC8 plays a critical positive regulatory role in waterlogging tolerance by maintaining cellular homeostasis and enhancing antioxidant capacity.

The Dof transcription factor family plays crucial roles in plant growth and stress responses. In this study, we identified 24 Dof genes (CcDof1–CcDof24) from the genome of Citrus clementina (Hort. ex Tan.). Phylogenetic analysis classified these proteins into six distinct clades, revealing evolutionary conservation with Dof members from Arabidopsis and tomato. Analysis of gene structure and conserved motifs showed that most CcDof genes are intronless or contain only a few introns, and their motif compositions are largely consistent with their phylogenetic relationships. Promoter analysis revealed a variety of cis-regulatory elements associated with light responsiveness, hormone signaling, and abiotic/biotic stress responses. Expression profiling demonstrated that CcDof genes exhibit tissue-specific expression patterns and are differentially regulated by various phytohormones (including ABA, SA, GA, and MeJA), low temperature stress, and infection by Phytophthora parasitica. Notably, transient overexpression of CcDof4 and CcDof6 in citrus leaves significantly enhanced resistance to P. parasitica, accompanied by upregulation of SA pathway markers NPR1 and PR1. Our findings provide a systematic characterization of the CcDof family and highlight the important roles of CcDof4 and CcDof6 in mediating citrus disease resistance, likely through modulation of the SA signaling pathway.