The American brackish water mussel, Mytella strigata (Hanley, 1843), is an invasive species with a growing global footprint, recently recorded in the Indian coastal ecosystems. Despite its rapid spread and potential ecological impact, no genetic data are available for Indian populations. We assessed the genetic diversity and population structure of M. strigata with a 683 bp fragment of the mitochondrial cytochrome b (cyt b) gene from 71 individuals collected from six locations along the Arabian Sea and the Bay of Bengal. Sixteen haplotypes were identified. The Vembanad lake and Ennore creek populations on the Kerala/West Coast and Tamil Nadu/East Coast, respectively, had the highest haplotype and nucleotide diversity, whereas otherWest and East Coast populations had very low diversity. AMOVA indicated that 16.7% of the genetic variance occurs among populations, which contrasts with the expectation for a species with a high dispersal of planktonic larvae. The haplotype network includes both shared and population-specific haplotypes, consistent with multiple introduction events and restricted gene flow rather than range expansion from a single source. Neutrality and mismatch analyses showed no significant evidence of demographic expansion, which likely reflects the limited resolution of the short cyt b fragment. The invasion history of M. strigata in India is complex, and is characterized by independent introductions, local diversification, and constrained post-settlement dispersal.

Nitrogen is a primary factor affecting the yield and quality of tobacco. Insufficient nitrogen results in poor tobacco output and poor leaf quality; in contrast, excessive nitrate can lead to delayed maturity and poor quality of cured tobacco leaves. To elucidate the molecular mechanism underlying the response of tobacco to low nitrogen, we conducted a multiomics analysis of tobacco plants treated with normal (7.5 mM) or low nitrogen (0.75 mM). Our results revealed that after 15 days of low-nitrate treatment, the plants exhibited stunted growth, yellowed leaves, and significant growth inhibition. The total nitrogen levels, and the activities of glutamine synthetase and nitrate reductase in the leaves also decreased significantly. Transcriptome analysis of the tobacco plants under low-nitrogen stress revealed 896 differentially expressed genes, with 404 genes upregulated and 492 genes downregulated in comparison with those in the control. Among the upregulated genes, the expression of Nitab4.5_0000970g0150, which is involved in galactose metabolism, significantly increased. Subsequent metabolome analysis revealed that 28 metabolites significantly changed under low-nitrogen treatment, including 23 metabolites whose levels increased and 6 whose levels decreased compared with those in the control. The increased metabolites were also enriched in galactose metabolism. Integrated transcriptome and metabolome analyses revealed that three pathways significantly changed- amino acid synthesis and metabolism, galactose metabolism and trehalose-6-phosphate metabolism-among which galactose metabolism is important for tobacco in response to low nitrogen stress. These findings provide a theoretical basis for further research on the function of nitrogen regulatory genes in tobacco and for the breeding of tobacco varieties with high nitrogen use efficiency.

Red tilapia has gained increasing popularity worldwide in the commercial aquaculture production due to its rapid growth and delightful taste. However, the occurrence of skin colour variation poses a significant challenge to the advancement of commercial culture. Furthermore, the molecular regulatory mechanism and genetic basis for the distinct skin colouration in red tilapia remain undisclosed. In this study, a comprehensive transcriptome analysis was conducted on red tilapia with different skin colour by integrating PacBio Iso-seq technology with Illumina short-read sequencing methods. A total of 41.38 Gb of clean data was generated, resulting in the acquisition of 30,970 transcripts. Among them, 10,829 transcripts were successfully annotated in at least one public database. In addition, 10,827 coding sequences, 452 transcription factors, and 781 lncRNAs were identified in new transcripts. Furthermore, we performed RNA-seq analysis to identify skin colour-associated genes in red tilapia with three colour spots (white spots, W; black spots, B; red spots, R). The results revealed the identification of 278 differentially expressed genes (DEGs) between the comparison groups, which included B vs R, B vs W, and WvsR.Amongthem, some known genes were found to be involved in regulating the skin pigment synthesis, including PMEL, Wnt-4, melanoregulin and ALK in red tilapia with different skin colour. In addition, some pathways, including melanogenesis (ko04916), ECMreceptor interaction (ko04512), Hedgehog signaling pathway (ko04340) and steroid hormone biosynthesis (ko00140), were associated with the skin pigment synthesis in red tilapia. Furthermore, the quantitative real-time PCR analysis confirmed a moderate correlation (coefficient of 0.68) between the results obtained from the qPCR and RNA-seq methodologies. In summary, our findings will significantly contribute to the enhanced comprehension of the molecular regulatory mechanisms underlying the variation in skin colour observed in red tilapia.