Fengyan Fang

Taraxacum kok-saghyz Rodin, an important rubber-producing plant, has emerged as a potential alternative crop for the natural rubber industry. Geranyl diphosphate synthase (GDS) catalyzes the condensation of dimethylallyl pyrophosphate and isopentenyl pyrophosphate into geranyl pyrophosphate in the mevalonate pathway in plants. However, its specific functions in natural rubber biosynthesis in T. kok-saghyz remain unclear. Methods: We conducted genome-wide analyses of TkGDS genes, followed by transient transformation assay, expression profiling, natural rubber quantification, and analysis of T. kok-saghyz photosynthesis. Results: Seven TkGDS genes are located on chromosomes A6 and A7 with an uneven distribution. All encoded TkGDS proteins contain FARM and SARM motifs. TkGDS1, TkGDS2, and TkGDS7 possess lspA domains, while TkGDS3, TkGDS4, TkGDS5, and TkGDS6 contain PLN02890 domains; both subgroups share similar domain architecture. TkGDS1, TkGDS2, and TkGDS7 exhibit interspecies collinearity with Arabidopsis thaliana; no intraspecies collinearity was detected. The putative cis-acting elements in promoter region of TkGDS genes mainly comprised abscisic acid responsiveness, anaerobic induction, light responsiveness, and MeJA responsiveness. Transient expression assays confirmed chloroplast localization of all TkGDS proteins. A strong positive correlation was observed between TkGDS1/TkGDS7 expression and natural rubber content, as confirmed by both transcriptome and qPCR analyses in T. kok-saghyz lines. Furthermore, overexpression of TkGDS1 and TkGDS7 improved photosynthetic efficiency and significantly increased natural rubber content (OE-TkGDS1: 6.08 ± 0.16%; OE-TkGDS7: 5.62 ± 0.32%; WT: 4.76 ± 0.28%). Conclusions: Our study elucidates the role of GDS1 and GDS7 in promoting growth and latex content, offering a genetic strategy for enhancing rubber accumulation in T. kok-saghyz.

Objectives: This study investigates the cpDNA sequences from six Hevea species, aiming to explore their genomic characteristics, gene content, and genetic relationships. The objectives include understanding the structure of these genomes, identifying potential gene rearrangements, and providing insights into genetic improvement and conservation strategies for the Hevea genus. Methods: cpDNA sequences from six Hevea species were sequenced and analyzed. Genome sizes, GC content, gene encoding potential, and structural integrity were assessed. Simple sequence repeats (SSRs) and codon usage were analyzed, with a focus on optimal codons and their frequency. Phylogenetic analysis was conducted to determine the genetic relationships within the Hevea genus. Results: The cpDNAs from the six species exhibited genome sizes ranging from 161,093 bp to 161,254 bp, with GC content between 35.72% and 35.75%. Each genome contained 91 to 92 protein-coding genes, with the infA gene consistently present. No significant gene rearrangements were detected, and SSR analysis revealed mono-repeats primarily composed of A/T bases. Codon usage analysis indicated that leucine is predominantly encoded by the UUA codon, and 31 optimal codons were identified, mainly ending in A or U. Phylogenetic analysis clarified the genetic relationships among the species. Conclusions: The study provides detailed insights into the cpDNA characteristics of Hevea species, highlighting stable genome structures, conserved genes, and specific patterns of codon usage. These findings are valuable for conservation efforts, genetic improvement strategies, and the sustainable use of Hevea germplasm.

Natural rubber is a crucial industrial material, and it is primarily harvested from the latex of the rubber tree Hevea brasiliensis by tapping the tree trunk. During the regular tapping process, mechanical damage seriously affects latex reproduction and rubber yield, but the molecular mechanisms on tapping stimulation remain unclear. In this study, we firstly determined the changed physiological markers on latex regeneration, overall latex yield, and latex flow time during the tapping process. Then, we combined proteomics and transcriptomics analyses of latex during tapping and identified 3940 differentially expressed genes (DEGs) and 193 differentially expressed proteins (DEPs). Among them, 773 DEGs and 120 DEPs displayed a persistent upregulation trend upon tapping. It is interesting that, in the detected transcription factors, basic helix-loop-helix (bHLH) family members occupied the highest proportion among all DEGs, and this trend was similarly observed in DEPs. Notably, 48 genes and 34 proteins related to natural rubber biosynthesis were identified, and most members of small rubber particle protein (SRPP) and rubber elongation factor (REF) showed a positive response to tapping stimulation. Among them, SRPP6 and REF5 showed significant and sustained upregulation at the gene and protein levels following tapping, indicating their pivotal roles for post-tapping rubber biosynthesis. Our results deepen the comprehension of the regulation mechanism underlying tapping and provide candidate genes and proteins for improving latex production in the Hevea rubber tree in future.

SINA (Seven in absentia) proteins in the subtype of E3 ubiquitin ligase family play a crucial role in plant growth and development. However, their functions in response to salt and osmotic stresses in oil crops are still largely unknown. In this study, a total number of 23 BnaSINAs were identified in the rapeseed genome. Chromosome location and collinear relationship analyses revealed that they were unevenly distributed on 13 chromosomes, and have gone through 22 segmental duplication events under purifying selection. Phylogenetic and gene structural analyses indicated that they belonged to five main groups, and those in the same subgroup showed similar gene structure. All BnaSINAs were predicted to form homo- or heterodimers. Except BnaSINA7, BnaSINA11, BnaSINA17 and BnaSINA18, which lacked the N-terminal RING finger, all BnaSINAs contained a conserved C-terminal SINA domain, a typical structural feature of the RING-type E3 ligase family. Transcriptional expression analyses demonstrated that most BnaSINAs were ubiquitously expressed in roots, stems, leaves, flowers, pods and seeds, and all were responsive to salt and osmotic stresses. Further, yeast two-hybrid and Arabidopsis mutant complementation analyses demonstrated that BnaSINA4 interacted with BnaSINA17 to form heterodimer, and expression of BnaSINA17 in the Arabidopsis sina2 mutant restored its growth resistance to salt and osmotic stresses. Our findings provide an important genetic foundation for the functional elucidation of BnaSINAs and a novel gene resource for the breeding of new oil crop cultivars with improved abiotic stress resistance.