Salt stress (SS) has become an important factor limiting afforestation programs. Because of their salt tolerance and fully sequenced genomes, poplars (Populus spp.) are used as model species to study SS mechanisms in trees. Here, we review recent insights into the physiological and molecular responses of Populus to SS, including ion homeostasis and signaling pathways, such as the salt overly sensitive (SOS) and reactive oxygen species (ROS) pathways. We summarize the genes that can be targeted for the genetic improvement of salt tolerance and propose future research areas.

Background Melaleuca alternifolia (Maiden & Betche) Cheel is a commercially important medicinal tea tree native to Australia. Tea tree oil (TTO), the essential oil distilled from its branches and leaves, has broad-spectrum germicidal activity and is highly valued in the pharmaceutical and cosmetic industries. Genome size is a key biology index, the study of which provides reference for genome engineering and sequencing work; besides, it also provides direct data for evolution biology and so on. Methods and results In the present study, the next-generation sequencing (NGS) was used to investigate the whole genome of Melaleuca alternifolia. 114 Gb high quality sequence data were obtained and assembled into 1,838,159 scafolds with an N50 length of 1021 bp. The assembled genome size is about 595 Mb, twice of that predicted by flow cytometer (300 Mb) and k-mer analysis (345 Mb). Benchmarking Universal Single-Copy Orthologs analyses indicated that only 11.3% of the conserved single-copy genes were miss. Repetitive regions cover over 40.43% of the genome. M. alternifolia maybe a diploid with highly heterozygous (heterozygosity is 0.8%). A total of 44,369 protein-coding genes were predicted in the assembled genome and 32,909 genes of these were functionally annotated, of which 8,436 genes were annotated in KEGG. Additionally, 457,661 simple sequence repeats (SSRs) and 1,109 transcription factors (TFs) form 67 TF families were identified in the assembled genome. Conclusion This draft genome may provide a reference for the deep sequencing strategies and be useful for future functional or comparative genomics analyses.

Background The tea tree (Melaleuca alternifolia) is renowned for its production of tea tree oil (TTO), an essential oil primarily composed of terpenes extracted from its shoot. MYB transcription factors, which are one of the largest TF families, play a crucial role in regulating primary and secondary metabolite synthesis. However, knowledge of the MYB gene family in M. alternifolia is limited. Methods and results Here, we conducted a comprehensive genome-wide analysis of MYB genes in M. alternifolia, referred to as MaMYBs, including phylogenetic relationships, structures, promoter regions, and GO annotations. Our findings classified 219 MaMYBs into four subfamilies: one 5R-MYB, four 3R-MYBs, sixty-one MYB-related, and the remaining 153 are all 2R-MYBs. Seven genes (MYB189, MYB146, MYB44, MYB29, MYB175, MYB162, and MYB160) were linked to terpenoid synthesis based on GO annotation. Phylogenetic analysis with Arabidopsis homologous MYB genes suggested that MYB193 and MYB163 may also be involved in terpenoid synthesis. Additionally, through correlation analysis of gene expression and metabolite content, we identified 42 MYB genes associated with metabolite content. Conclusion The results provide valuable insights into the importance of MYB transcription factors in essential oil production in M. alternifolia. These findings lay the groundwork for a better understanding of the MYB regulatory network and the development of novel strategies to enhance essential oil synthesis in M. alternifolia.