Eremosparton songoricum (Litv.) Vass. is a rare leafless legume shrub endemic to central Asia which grows on bare sand. It shows extreme drought tolerance and is being developed as a model organism for investigating morphological, physiological, and molecular adaptations to harsh desert environments. APETALA2/Ethylene Responsive Factor (AP2/ERF) is a large plant transcription factor family that plays important roles in plant responses to various biotic and abiotic stresses and has been extensively studied in several plants. However, our knowledge on the AP2/ERF family in legume species is limited, and no respective study was conducted so far on the desert shrubby legume E. songoricum. Here, 153 AP2/ERF genes were identified based on the E. songoricum genome data. EsAP2/ERFs covered AP2 (24 genes), DREB (59 genes), ERF (68 genes), and Soloist (2 genes) subfamilies, and lacked canonical RAV subfamily genes based on the widely used classification method. The DREB and ERF subfamilies were further divided into A1–A6 and B1–B6 groups, respectively. Protein motifs and exon-intron structures of EsAP2/ERFs were also examined, which matched the subfamily/group classification. Cis-acting element analysis suggested that EsAP2/ERF genes shared many stress- and hormone-related cis-regulatory elements. Moreover, the gene numbers and the ratio of each subfamily and the intron-exon structures were systematically compared with other model plants ranging from algae to angiosperms, including ten legumes. Our results supported the view that AP2 and ERF evolved early and already existed in algae, whereas RAV and DREB began to appear in moss species. Almost all plant AP2 and Soloist genes contained introns, whereas most DREB and ERF genes did not. The majority of EsAP2/ERFs were induced by drought stress based on RNA-seq data, EsDREBs were highly induced and had the largest number of differentially expressed genes in response to drought. Eight out of twelve representative EsAP2/ERFs were significantly up-regulated as assessed by RT-qPCR. This study provides detailed insights into the classification, gene structure, motifs, chromosome distribution, and gene expression of AP2/ERF genes in E. songoricum and lays a foundation for better understanding of drought stress tolerance mechanisms in legume plants. Moreover, candidate genes for drought-resistant plant breeding are proposed.

Among the most important transcription factors in plants, the v-myb avian myeloblastosis viral oncogene homolog (MYB) regulates the expression network of response genes under stresses such as fungal infection. In China, the canker disease Valsa mali threatens the survival of Malus sieversii, an ancestor of cultivated apples. Using the M. sieversii genome, we identified 457 MsMYB and 128 R2R3-MsMYB genes that were randomly distributed across 17 chromosomes. Based on protein sequence and structure, the R2R3-MsMYB genes were phylogenetically divided into 29 categories, and 26 conserved motifs were identified. We further predicted cis-elements in the 2000-kb promoter region of R2R3-MsMYBs based on the genome. Transcriptome analysis of M. sieversii under V. mali infection showed that 27 R2R3-MsMYBs were significantly differentially expressed, indicating their key role in the response to V. mali infection. Using transient transformation, MsMYB14, MsMYB24, MsMYB39, MsMYB78, and MsMYB108, which were strongly induced by V. mali infection, were functionally identified. Among the five MsMYBs, MsMYB14 and MsMYB78 were both important in enhancing resistance to diseases, whereas MsMYB24 inhibited resistance. Based on the results of this study, we gained a better understanding of the MsMYB transcription factor family and laid the foundation for a future research program on disease prevention strategies in M. sieversii.

Syntrichia caninervis is a desiccation tolerant moss and is the dominant bryophyte found in biological soil crusts in the Gurbantunggut desert. In this study, we assessed the transcriptome profiles of S. caninervis gametophytes during the dehydration-rehydration (D-R) process (across 9 time points) using Illumina sequencing. In total, 22489 transcripts were identified, including 5337 novel transcripts, that mapped to the reference genome. A total of 12548 transcripts exhibited significant alterations in the D-R samples compared with the control samples. The differentially expressed transcripts (DETs) possessed several enriched Gene Ontology terms, such as “water stress response”, “oxidation-reduction process”, “membrane metabolism”, “photosynthesis”, and “transcription factor activity”. Moreover, during early dehydration stress, the DETs were significantly enriched in stress-related pathways from the Kyoto Encyclopedia of Genes and Genomes, such as “phenylpropanoid biosynthesis”, “alpha-linolenic acid metabolism”, and “fructose and mannose metabolism”. Photosynthesis-related transcripts (e.g., ScPsa H, ScRubisco, and ScLhcb1) were inhibited during the dehydration treatment and significantly accumulated during the late rehydration period. Most transcripts from the late embryogenesis abundant proteins (LEA) and early light-inducible protein (ELIP) families strongly accumulated at the late dehydration stage. These pathways were positively correlated with the content changes of absolute water content and Fv/Fm values, alongside peroxidase and superoxide dismutase activities. Seven transcription factor families, including AP2-ERF, bHLH, G2-like, MYB, NAC, WRKY, and bZIP, were enriched in DETs during D-R treatment. This study is the first transcriptome analysis using the S. caninervis genome for gene annotation and multigroup D-R treatment points. Our results demonstrated the detailed dynamic changes in the transcriptome of S. caninervis during the D-R process. These results also improve understanding of desiccation tolerant plants’ adaptations to desiccation stress at the transcription level and provide promising gene resources for transgenic crop breeding.