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Background: WRKY transcription factors play pivotal roles in regulating plant multiple abiotic stress tolerance, however, a genome-wide systematical analysis of WRKY genes in sweetpotato is still missing., Results: Herein, 84 putative IbWRKYs with WRKY element sequence variants were identified in sweetpotato reference genomes. Fragment duplications, rather than tandem duplications, were shown to play prominent roles in IbWRKY gene expansion. The collinearity analysis between IbWRKYs and the related orthologs from other plants further depicted evolutionary insights into IbWRKYs. Phylogenetic relationships displayed that IbWRKYs were divided into three main groups (I, II and III), with the support of the characteristics of exon-intron structures and conserved protein motifs. The IbWRKY genes, mainly from the group Ib, displayed remarkable and diverse expression profiles under multiple abiotic stress (NaCl, PEG6000, cold and heat) and hormone (ABA, ACC, JA and SA) treatments, which were determined by RNA-seq and qRT-PCR assays, suggesting their potential roles in mediating particular stress responses. Moreover, IbWRKY58L could interact with IbWRKY82 as revealed by yeast two-hybrid based on the protein interaction network screening. And abiotic stress-remarkably induced IbWRKY21L and IbWRKY51 were shown to be localized in the nucleus and had no transactivation activities., Conclusion: These results provide valuable insights into sweetpotato IbWRKYs and will lay a foundation for further exploring functions and possible regulatory mechanisms of IbWRKYs in abiotic stress tolerance., (© 2022. The Author(s).)

Background: The plant-specific GRAS transcription factors play pivotal roles in various adverse environmental conditions. Numerous GRAS genes have been explored and characterized in different plants, however, comprehensive survey on GRASs in sweetpotato is lagging., Results: In this study, 72 putative sweetpotato IbGRAS genes with uneven distribution were isolated on 15 chromosomes and classified into 12 subfamilies supported by gene structures and motif compositions. Moreover, both tandem duplication and segmental duplication events played critical roles in the expansion of sweetpotato GRAS genes, and the collinearity between IbGRAS genes and the related orthologs from nine other plants further depicted evolutionary insights into GRAS gene family. RNA-seq analysis under salt stress and qRT-PCR detection of 12 selected IbGRAS genes demonstrated their significant and varying inductions under multiple abiotic stresses (salt, drought, heat and cold) and hormone treatments (ABA, ACC and JA). Consistently, the promoter regions of IbGRAS genes harbored a series of stress- and hormone-associated cis-acting elements. Among them, IbGRAS71, the potential candidate for breeding tolerant plants, was characterized as having transactivation activity in yeasts, while IbGRAS-2/-4/-9 did not. Moreover, a complex interaction relationship between IbGRASs was observed through the interaction network analysis and yeast two-hybrid assays., Conclusions: Our results laid a foundation for further functional identifications of IbGRAS genes, and multiple members may serve as potential regulators for molecular breeding of tolerant sweetpotato., (© 2022. The Author(s).)

The AP2/ERF transcription factors (TFs) regulate various processes of plant growth, development, and response to environmental stimuli. Although they have been extensively documented in many plants, little is known about stress responsive APETALA2/ethylene response factor (AP2/ERF) genes in sweetpotato (Ipomoea batatas L.). In this study, 20 putative AP2/ERF genes, named IbERF1, IbERF2, and IbERF5–IbERF23 were identified based on the salt‐treated RNA‐seq data from two sweetpotato cultivars with different salt tolerance. Phylogenetic analysis and sequence characterization identified that all the screened IbERF proteins contained a conserved AP2 domain, which belonged to dehydration‐responsive element binding proteins (DREB; 7 members) or ERF (13 members) subfamily. The systematic expression analysis of 12 mainly salt‐induced IbERFs by quantitative real‐time polymerase chain reaction (qRT‐PCR) revealed that most IbERFs were remarkably increased by multiple abiotic stresses, such as NaCl, dehydration, and cold stress. Furthermore, varying degrees of upregulation were also detected in the expression of most IbERFs when treated with hormone abscisic acid, jasmonic acid, and salicylic acid. The expression profiles of IbERFs corroborate their involvement in diverse biological processes. In addition, the IbERF5, which was exclusively upregulated by the treatments, was identified as a nuclear protein without transcriptional activation activity. Collectively, the data of stress responsive IbERFs will provide valuable knowledge for further functional studies of IbERFs in sweetpotato stress tolerance. [ABSTRACT FROM AUTHOR]

Siyuan Liu, Chengbin Zhang and Fen Guo contributed equally to this work. Reference 1 Liu S, Zhang C, Guo F. A systematical genome-wide analysis and screening of WRKY transcription factor family engaged in abiotic stress response in sweetpotato. [Extracted from the article]

Background: Basic region/leucine zipper (bZIP) transcription factors perform as crucial regulators in ABA-mediated stress response in plants. Nevertheless, the functions for most bZIP family members in tomato remain to be deciphered. Results: Here we examined the functional characterization of SlbZIP1 under salt and drought stresses in tomato. Silencing of SlbZIP1 in tomato resulted in reduced expression of multiple ABA biosynthesis- and signal transduction-related genes in transgenic plants. In stress assays, SlbZIP1-RNAi transgenic plants exhibited reduced tolerance to salt and drought stresses compared with WT plants, as are evaluated by multiple physiological parameters associated with stress responses, such as decreased ABA, chlorophyll contents and CAT activity, and increased MDA content. In addition, RNA-seq analysis of transgenic plants revealed that the transcription levels of multiple genes encoding defense proteins related to responses to abiotic stress (e.g. endochitinase, peroxidases, and lipid transfer proteins) and biotic stress (e.g. pathogenesis-related proteins) were downregulated in SlbZIP1-RNAi plants, suggesting that SlbZIP1 plays a role in regulating the genes related to biotic and abiotic stress response. Conclusions: Collectively, the data suggest that SlbZIP1 exerts an essential role in salt and drought stress tolerance through modulating an ABA-mediated pathway, and SlbZIP1 may hold potential applications in the engineering of salt- and drought-tolerant tomato cultivars. [ABSTRACT FROM AUTHOR]

Basic region/leucine zipper (bZIP) transcription factors function as critical regulators in numerous abiotic stress responses. Massive bZIPs have been systematically identified in plants, but not in sweetpotato. In this study, 87 sweetpotato IbbZIPs unevenly distributed onto 15 chromosomes were identified, and segmental duplications were shown to play dominant roles in the diversity of IbbZIPs. The collinearity between IbbZIPs and the related orthologs from nine plants depicted evolutionary insights into bZIP gene family. Additionally, IbbZIP proteins were clustered into 11 subfamilies while no members were found in the M subfamily, and the regularity of gene structures and conserved motifs was consistent with the subgroup classification. Evidence from transcriptome data and qRT-PCR analysis of 12 selected IbbZIPs revealed that they were significantly and varyingly induced under multiple abiotic stresses (salt, drought, heat and cold) and hormone treatments (ABA, ACC, JA and SA). Consistently, the promoters of IbbZIPs harbored multiple stress- and hormone-related cis-acting elements. Besides, IbbZIP17 and IbbZIP61 exhibited transactivation activity in yeasts, while IbbZIP-14/-69/-84 did not. These findings supply worthy foundations for further functional investigation of IbbZIPs , and multiple members may serve as promising regulators to enhance the abiotic stress tolerance of transgenic plants. [ABSTRACT FROM AUTHOR]

• 175 sweetpotato IbANCs were identified and clustered into 22 subgroups including 4 specific subgroups. • Tandem duplications and segmental duplications played critical roles in the diversity of IbANCs. • Collinearity between IbANCs and related orthologs from other plants depicted evolutionary insights into NACs. • Transcriptome and qRT-PCR data provided multiple promising IbNAC regulators for breeding tolerant sweetpotato. • IbNAC006 and IbNAC143 exhibited transactivation activities in yeasts. Sweetpotato is a pivotal crop that can tolerate various edaphic and climatic conditions. The plant-specific NAC transcription factors are involved in regulating various adverse environmental conditions, while currently NAC genes have not been systematically characterized in sweetpotato. Herein, 175 putative NAC or NAC-like genes (IbNACs) were identified in sweetpotato. These genes were unevenly scattered onto all 15 chromosomes, among which 12 pairs of tandem duplications and 12 groups of fragment duplications existed. The collinearity analysis between IbNACs and the related orthologs from nine other plant species further depicted evolutionary insights into NAC gene family. Phylogenetic analysis displayed that IbNAC proteins were classified into 22 subfamilies including four sweetpotato-specific subfamilies, with the support of gene structure and motif analyses. Transcriptome analysis showed that IbNAC genes differed significantly in expression under salt stress, and significant and varying expression of ten selected genes under multiple abiotic stresses was detected by qRT-PCR. Moreover, IbNAC006 and IbNAC143, which were significantly induced by abiotic stress, exhibited obvious transactivation activities, while IbNAC-029/-138/-148 did not. These results will lay the foundation for further evolutionary analysis and functional characterization of IbNACs , particularly with regards to the potential applications of multiple IbNAC regulators in the breeding of tolerant sweetpotato. [ABSTRACT FROM AUTHOR]