Transcriptome- and genome-wide systematic identification of expansin gene family and their expression in tuberous root development and stress responses in sweetpotato (Ipomoea batatas).

Introduction: Expansins (EXPs) are essential components of the plant cell wall that function as relaxation factors to directly promote turgor-driven expansion of the cell wall, thereby controlling plant growth and development and diverse environmental stress responses. EXPs genes have been identified and characterized in numerous plant species, but not in sweetpotato. Results and methods: In the present study, a total of 59 EXP genes unevenly distributed across 14 of 15 chromosomes were identified in the sweetpotato genome, and segmental and tandem duplications were found to make a dominant contribution to the diversity of functions of the IbEXP family. Phylogenetic analysis showed that IbEXP members could be clustered into four subfamilies based on the EXPs from Arabidopsis and rice, and the regularity of protein motif, domain, and gene structures was consistent with this subfamily classification. Collinearity analysis between IbEXP genes and related homologous sequences in nine plants provided further phylogenetic insights into the EXP gene family. Cis-element analysis further revealed the potential roles of IbEXP genes in sweetpotato development and stress responses. RNA-seq and qRT-PCR analysis of eight selected IbEXPs genes provided evidence of their specificity in different tissues and showed that their transcripts were variously induced or suppressed under different hormone treatments (abscisic acid, salicylic acid, jasmonic acid, and 1-aminocyclopropane-1-carboxylic acid) and abiotic stresses (low and high temperature). Discussion: These results provide a foundation for further comprehensive investigation of the functions of IbEXP genes and indicate that several members of this family have potential applications as regulators to control plant development and enhance stress resistance in plants.

First systematic review of the last 30 years of research on sweetpotato: elucidating the frontiers and hotspots.

Sweetpotato is an economically important crop, and it has various advantages over other crops in addressing global food security and climate change. Although substantial articles have been published on the research of various aspects of sweetpotato biology, there are no specific reports to systematically crystallize the research achievements. The current review takes the lead in conducting a keyword-centric spatiotemporal dimensional bibliometric analysis of articles on sweetpotato research using CiteSpace software to comprehensively clarify the development status, research hotspot, and development trend in the past 30 years (1993-2022). Quantitative analysis was carried out on the publishing countries, institutions, disciplines, and scholars to understand the basic status of sweetpotato research; then, visual analysis was conducted on high-frequency keywords, burst keywords, and keyword clustering; the evolution of major research hotspots and the development trend in different periods were summarized. Finally, the three main development stages-preliminary stage (1993-2005), rapid stage (2006-2013), and diversified mature stage (2014-2022)-were reviewed and analyzed in detail. Particularly, the development needs of sweetpotato production in improving breeding efficiency, enhancing stress tolerance, coordinating high yield with high quality and high resistance, and promoting demand were discussed, which will help to comprehensively understand the development dynamics of sweetpotato research from different aspects of biological exploration.

A SEPALLATA MADS-Box Transcription Factor, SlMBP21, Functions as a Negative Regulator of Flower Number and Fruit Yields in Tomato.

MADS-box transcription factors act as the crucial regulators in plant organ differentiation. Crop yields are highly influenced by the flower number and fruit growth. However, flower identification is a very complex biological process, which involves many cascade regulations. The molecular mechanisms underlying the genetic regulation of flower identification in cultivated plants, such as tomato, are intricate and require further exploration. In this study, we investigated the vital function of a SEPALLATA (SEP) MADS-box gene, SlMBP21, in tomato sympodial inflorescence meristem (SIM) development for the conversion from SIMs to floral meristems (FMs). SlMBP21 transcripts were primarily accumulated in young inflorescence meristem, flowers, sepals, and abscission zones. The Ailsa Craig (AC++) tomato plants with suppressed SlMBP21 mRNA levels using RNAi exhibited a large increase in flower number and fruit yields in addition to enlarged sepals and inhibited abscission zone development. Scanning electron microscopy (SEM) revealed that the maturation of inflorescence meristems (IMs) was repressed in SlMBP21-RNAi lines. RNA-seq and qRT-PCR analyses showed that numerous genes related to the flower development, plant hormone signal transduction, cell cycle, and cell proliferation et al. were dramatically changed in SlMBP21-RNAi lines. Yeast two-hybrid assay exhibited that SlMBP21 can respectively interact with SlCMB1, SFT, JOINTLESS, and MC, which play key roles in inflorescence meristems or FM development. In summary, our data demonstrate that SlMBP21 functions as a key regulator in SIM development and the conversion from SIMs to FMs, through interacting with other regulatory proteins to control the expression of related genes.

Genome-wide systematic survey and analysis of the RNA helicase gene family and their response to abiotic stress in sweetpotato.

Sweetpotato (Ipomoea batatas (L.) Lam.) holds a crucial position as one of the staple foods globally, however, its yields are frequently impacted by environmental stresses. In the realm of plant evolution and the response to abiotic stress, the RNA helicase family assumes a significant role. Despite this importance, a comprehensive understanding of the RNA helicase gene family in sweetpotato has been lacking. Therefore, we conducted a comprehensive genome-wide analysis of the sweetpotato RNA helicase family, encompassing aspects such as chromosome distribution, promoter elements, and motif compositions. This study aims to shed light on the intricate mechanisms underlying the stress responses and evolutionary adaptations in sweetpotato, thereby facilitating the development of strategies for enhancing its resilience and productivity. 300 RNA helicase genes were identified in sweetpotato and categorized into three subfamilies, namely IbDEAD, IbDEAH and IbDExDH. The collinearity relationship between the sweetpotato RNA helicase gene and 8 related homologous genes from other species was explored, providing a reliable foundation for further study of the sweetpotato RNA helicase gene family's evolution. Furthermore, through RNA-Seq analysis and qRT-PCR verification, it was observed that the expression of eight RNA helicase genes exhibited significant responsiveness to four abiotic stresses (cold, drought, heat, and salt) across various tissues of ten different sweetpotato varieties. Sweetpotato transgenic lines overexpressing the RNA helicase gene IbDExDH96 were generated using A.rhizogenes-mediated technology. This approach allowed for the preliminary investigation of the role of sweetpotato RNA helicase genes in the response to cold stress. Notably, the promoters of RNA helicase genes contained numerous cis-acting elements associated with temperature, hormone, and light response, highlighting their crucial role in sweetpotato abiotic stress response.

Systematic identification and expression analysis of bHLH gene family reveal their relevance to abiotic stress response and anthocyanin biosynthesis in sweetpotato.

BACKGROUND: bHLH transcription factors play significant roles in regulating plant growth and development, stress response, and anthocyanin biosynthesis. Sweetpotato is a pivotal food and industry crop, but little information is available on sweetpotato bHLH genes. RESULTS: Herein, 227 putative IbbHLH genes were defined on sweetpotato chromosomes, and fragment duplications were identified as the dominant driving force for IbbHLH expansion. These IbbHLHs were divided into 26 subfamilies through phylogenetic analysis, as supported by further analysis of exon-intron structure and conserved motif composition. The syntenic analysis between IbbHLHs and their orthologs from other plants depicted evolutionary relationships of IbbHLHs. Based on the transcriptome data under salt stress, the expression of 12 IbbHLHs was screened for validation by qRT-PCR, and differential and significant transcriptions under abiotic stress were detected. Moreover, IbbHLH123 and IbbHLH215, which were remarkably upregulated by stress treatments, had obvious transactivation activity in yeasts. Protein interaction detections and yeast two-hybrid assays suggested an intricate interaction correlation between IbbHLHs. Besides, transcriptome screening revealed that multiple IbbHLHs may be closely related to anthocyanin biosynthesis based on the phenotype (purple vs. white tissues), which was confirmed by subsequent qRT-PCR analysis. CONCLUSIONS: These results shed light on the promising functions of sweetpotato IbbHLHs in abiotic stress response and anthocyanin biosynthesis.

Comparative Analysis of the PYL Gene Family in Three Ipomoea Species and the Expression Profiling of IbPYL Genes during Abiotic Stress Response in Sweetpotato.

Abscisic acid (ABA), a critical phytohormone that regulates plant development and stress response, is sensed by the ABA receptors PYR/PYL/RCAR (PYLs). The PYL genes have been widely studied in multiple plant species, while a systematic analysis of PYL genes in the genus Ipomoea remains unperformed. Here, a total of 13, 14, and 14 PYLs were identified in Ipomoea batatas, Ipomoea trifida, and Ipomoea triloba, respectively. Fragment duplication was speculated to play prominent roles in Ipomoea PYL gene expansions. These Ipomoea PYLs were classified into three subfamilies via phylogenetic analysis, which was supported by exon-intron structures and conserved motif analyses. Additionally, the interspecies collinearity analysis further depicted a potential evolutionary relationship between them. Moreover, qRT-PCR analysis showed that multiple IbPYLs are highly and differentially responsive to abiotic stress treatments, suggesting their potential roles in sweetpotato stress responses. Taken together, these data provide valuable insights into the PYLs in the genus Ipomoea, which may be useful for their further functional analysis of their defense against environmental changes.

Genome-wide survey and expression analysis of Dof transcription factor family in sweetpotato shed light on their promising functions in stress tolerance.

DNA-binding with one finger (Dof) transcription factors play a crucial role in plant abiotic stress regulatory networks, although massive Dofs have been systematically characterized in plants, they have not been identified in the hexaploid crop sweetpotato. Herein, 43 IbDof genes were detected to be disproportionally dispersed across 14 of the 15 chromosomes of sweetpotato, and segmental duplications were discovered to be the major driving force for the expansion of IbDofs. The collinearity analysis of IbDofs with their related orthologs from eight plants revealed the potential evolutionary history of Dof gene family. Phylogenetic analysis displayed that IbDof proteins were assigned into nine subfamilies, and the regularity of gene structures and conserved motifs was consistent with the subgroup classification. Additionally, five chosen IbDof genes were shown to be substantially and variably induced under various abiotic conditions (salt, drought, heat, and cold), as well as hormone treatments (ABA and SA), according to their transcriptome data and qRT-PCR experiments. Consistently, the promoters of IbDofs contained a number of cis-acting elements associated with hormone and stress responses. Besides, it was noted that IbDof2 had transactivation activity in yeasts, while IbDof-11/-16/-36 did not, and protein interaction network analysis and yeast two-hybrid experiments revealed a complicated interaction connection amongst IbDofs. Collectively, these data lay a foundation for further functional explorations of IbDof genes, especially with regards to the possible application of multiple IbDof members in breeding the tolerant plants.

The unique sweet potato NAC transcription factor IbNAC3 modulates combined salt and drought stresses.

Plants often simultaneously experience combined stresses rather than a single stress, causing more serious damage, but the underlying mechanisms remain unknown. Here, we identified the stress-induced IbNAC3 from sweet potato (Ipomoea batatas) as a nucleus-localized transcription activator. IbNAC3 contains a unique activation domain whose MKD sequence confers transactivation activities to multiple other TFs and is essential for the activated expression of downstream target genes. Ectopic expression of IbNAC3 conferred tolerance to single and combined salt and drought stresses in Arabidopsis (Arabidopsis thaliana), and a group of NAM, ATAF1/2, and CUC2 (NAC) TFs, including ANAC011, ANAC072, ANAC083, ANAC100, and NAP, interacted with IbNAC3, and the specific domains responsible for each interaction varied. Intriguingly, IbNAC3 repressed the interaction among the five NACs, and knockout or mutation of ANAC011 and ANAC072 dramatically impaired combined stress tolerance. IbNAC3-ANAC072 and IbNAC3-NAP modules synergistically activated the MICROTUBULE-RELATED E3 LIGASE57 (MREL57) gene. Consistently, mutation of MREL57 and overexpression of WAVE-DAM-PENED2-LIKE7, encoding a target protein of MREL57, both remarkably impaired combined stress tolerance. Moreover, transgenic plants displayed abscisic acid (ABA) hyposensitivity by directly promoting the transcription of ENHANCED RESPONSE TO ABA 1, a key negative regulator of ABA signaling. The data unravel the unique IbNAC3 TF functions as a pivotal component in combined stress tolerance by integrating multiple regulatory events and ubiquitin pathways, which is essential for developing high-tolerant plants in natural environments.

A systematical genome-wide analysis and screening of WRKY transcription factor family engaged in abiotic stress response in sweetpotato.

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.

Genetic and Genomic Research on Sweet Potato for Sustainable Food and Nutritional Security.

Food security is the main challenge to the developing world, especially in the least developed countries [...].

Comparative Analysis of Salt Responsive MicroRNAs in Two Sweetpotato [Ipomoea batatas (L.) Lam.] Cultivars With Different Salt Stress Resistance.

Sweetpotato [Ipomoea batatas (L.) Lam.] is an important food, vegetable and economic crop, but its productivity is remarkably affected by soil salinity. MiRNAs are a class of endogenous non-coding small RNAs that play an important role in plant resistance to salt stress. However, the function of miRNAs still remains largely unknown in sweetpotato under salt stress. Previously, we identified salt-responsive miRNAs in one salt-sensitive sweetpotato cultivar "Xushu 32." In this study, we identified miRNAs in another salt-tolerant cultivar "Xushu 22" by high-throughput deep sequencing and compared the salt-responsive miRNAs between these two cultivars with different salt sensitivity. We identified 687 miRNAs in "Xushu 22," including 514 known miRNAs and 173 novel miRNAs. Among the 759 miRNAs from the two cultivars, 72 and 109 miRNAs were specifically expressed in "Xushu 32" and "Xushu 22," respectively, and 578 miRNAs were co-expressed. The comparison of "Xushu 32" and "Xushu 22" genotypes showed a total of 235 miRNAs with obvious differential expression and 177 salt-responsive miRNAs that were obviously differently expressed between "Xushu 32" and "Xushu 22" under salt stress. The target genes of the miRNAs were predicted and identified using the Target Finder tool and degradome sequencing. The results showed that most of the targets were transcription factors and proteins related to metabolism and stress response. Gene Ontology analysis revealed that these target genes are involved in key pathways related to salt stress response and secondary redox metabolism. The comparative analysis of salt-responsive miRNAs in sweetpotato cultivars with different salt sensitivity is helpful for understanding the regulatory pattern of miRNA in different sweetpotato genotypes and improving the agronomic traits of sweetpotato by miRNA manipulation in the future.

Overexpression of an Inositol Phosphorylceramide Glucuronosyltransferase Gene IbIPUT1 Inhibits Na+ Uptake in Sweet Potato Roots.

IPUT1 is a glycosyltransferase capable of synthesizing the glycosyl inositol phosphorylceramide (GIPC) sphingolipid. The GIPC sphingolipid is a Na+ receptor on cell membranes which can sense extracellular Na+ concentrations, promote the increase in intracellular Ca2+ concentrations, and plays critical roles in maintaining intracellular Na+ balance. Therefore, the IPUT1 gene plays an important role in the genetic improvement of crop salt tolerance. Herein, the IbIPUT1 gene, which encodes an ortholog of Arabidopsis AtIPUT1, from sweet potato was cloned. Agrobacterium rhizogenes-mediated in vivo transgenic technology, non-invasive micro-measuring technology (NMT) and Na+ fluorescence imaging technology were then combined to quickly study the potential function of IbIPUT1 in salt tolerance. The data showed that IbIPUT1 was involved in the regulation of root cell Na+ balance, and the overexpression of IbIPUT1 could not promote sweet potato root cell Na+ efflux under salt stress, but it could significantly inhibit the Na+ absorption of root cells, thereby reducing the accumulation of Na+ in root cells under salt stress. Additionally, Ca2+ efflux in transgenic root cells was slightly higher than that in control roots under salt stress. Collectively, an efficient transgenic method for gene function studies was established, and our results suggested that IbIPUT1 acts as a candidate gene for the genetic enhancement of sweet potato salt tolerance.

Genome-wide survey and expression analysis of GRAS transcription factor family in sweetpotato provides insights into their potential roles in stress response.

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.

Molecular Characterization and Target Prediction of Candidate miRNAs Related to Abiotic Stress Responses and/or Storage Root Development in Sweet Potato.

Sweet potato is a tuberous root crop with strong environmental stress resistance. It is beneficial to study its storage root formation and stress responses to identify sweet potato stress- and storage-root-thickening-related regulators. Here, six conserved miRNAs (miR156g, miR157d, miR158a-3p, miR161.1, miR167d and miR397a) and six novel miRNAs (novel 104, novel 120, novel 140, novel 214, novel 359 and novel 522) were isolated and characterized in sweet potato. Tissue-specific expression patterns suggested that miR156g, miR157d, miR158a-3p, miR167d, novel 359 and novel 522 exhibited high expression in fibrous roots or storage roots and were all upregulated in response to storage-root-related hormones (indole acetic acid, IAA; zeaxanthin, ZT; abscisic acid, ABA; and gibberellin, GAs). The expression of miR156g, miR158a-3p, miR167d, novel 120 and novel 214 was induced or reduced dramatically by salt, dehydration and cold or heat stresses. Moreover, these miRNAs were all upregulated by ABA, a crucial hormone modulator in regulating abiotic stresses. Additionally, the potential targets of the twelve miRNAs were predicted and analyzed. Above all, these results indicated that these miRNAs might play roles in storage root development and/or stress responses in sweet potato as well as provided valuable information for the further investigation of the roles of miRNA in storage root development and stress responses.

The tomato OST1-VOZ1 module regulates drought-mediated flowering.

Flowering is a critical agricultural trait that substantially affects tomato fruit yield. Although drought stress influences flowering time, the molecular mechanism underlying drought-regulated flowering in tomato remains elusive. In this study, we demonstrated that loss of function of tomato OPEN STOMATA 1 (SlOST1), a protein kinase essential for abscisic acid (ABA) signaling and abiotic stress responses, lowers the tolerance of tomato plants to drought stress. slost1 mutants also exhibited a late flowering phenotype under both normal and drought stress conditions. We also established that SlOST1 directly interacts with and phosphorylates the NAC (NAM, ATAF and CUC)-type transcription factor VASCULAR PLANT ONE-ZINC FINGER 1 (SlVOZ1), at residue serine 67, thereby enhancing its stability and nuclear translocation in an ABA-dependent manner. Moreover, we uncovered several SlVOZ1 binding motifs from DNA affinity purification sequencing analyses and revealed that SlVOZ1 can directly bind to the promoter of the major flowering-integrator gene SINGLE FLOWER TRUSS to promote tomato flowering transition in response to drought. Collectively, our data uncover the essential role of the SlOST1-SlVOZ1 module in regulating flowering in response to drought stress in tomato and offer insights into a novel strategy to balance drought stress response and flowering.

A domesticated Harbinger transposase forms a complex with HDA6 and promotes histone H3 deacetylation at genes but not TEs in Arabidopsis.

In eukaryotes, histone acetylation is a major modification on histone N-terminal tails that is tightly connected to transcriptional activation. HDA6 is a histone deacetylase involved in the transcriptional regulation of genes and transposable elements (TEs) in Arabidopsis thaliana. HDA6 has been shown to participate in several complexes in plants, including a conserved SIN3 complex. Here, we uncover a novel protein complex containing HDA6, several Harbinger transposon-derived proteins (HHP1, SANT1, SANT2, SANT3, and SANT4), and MBD domain-containing proteins (MBD1, MBD2, and MBD4). We show that mutations of all four SANT genes in the sant-null mutant cause increased expression of the flowering repressors FLC, MAF4, and MAF5, resulting in a late flowering phenotype. Transcriptome deep sequencing reveals that while the SANT proteins and HDA6 regulate the expression of largely overlapping sets of genes, TE silencing is unaffected in sant-null mutants. Our global histone H3 acetylation profiling shows that SANT proteins and HDA6 modulate gene expression through deacetylation. Collectively, our findings suggest that Harbinger transposon-derived SANT domain-containing proteins are required for histone deacetylation and flowering time control in plants.

Exogenous Melatonin Attenuates Post-Harvest Decay by Increasing Antioxidant Activity in Wax Apple (Syzygium samarangense).

Wax apple is one of the most popular tropical fruit but undergoes serious post-harvest decay during storage, transportation and marketing. Melatonin (MT) plays important roles in plant growth, development and stress responses. However, its function in post-harvest preservation of fruit remains largely unknown. In the present study, the physiological function and molecular mechanism of exogenous MT for post-harvest preservation were evaluated in wax apple fruit. Results showed that MT treatment remarkably reduced decay incidence and the accumulation of excess reactive oxygen species (ROS) but increased the activity of antioxidant enzymes, suggesting that exogenous MT alleviates the post-harvest decay of wax apple by regulating the balance between ROS production and antioxidant system. Meanwhile, the gene expression was analyzed by transcriptome confirmed by quantitative PCR. This study provides insights into the regulatory mechanism and proper application strategies for post-harvest preservation of wax apple and other fruits though melatonin manipulation.

Comparative Transcriptome and Proteome Analysis of Salt-Tolerant and Salt-Sensitive Sweet Potato and Overexpression of IbNAC7 Confers Salt Tolerance in Arabidopsis.

Salt stress is one of the major devastating factors affecting the growth and yield of almost all crops, including the crucial staple food crop sweet potato. To understand their molecular responses to salt stress, comparative transcriptome and proteome analysis of salt-tolerant cultivar Xushu 22 and salt-sensitive cultivar Xushu 32 were investigated. The results showed the two genotypes had distinct differences at the transcription level and translation level even without salt stress, while inconsistent expression between the transcriptome and proteome data was observed. A total of 16,396 differentially expressed genes (DEGs) and 727 differentially expressed proteins (DEPs) were identified. Wherein, 1,764 DEGs and 93 DEPs were specifically expressed in the tolerant genotype. Furthermore, the results revealed that the significantly upregulated genes were mainly related to the regulation of ion accumulation, stress signaling, transcriptional regulation, redox reactions, plant hormone signal transduction, and secondary metabolite accumulation, which may be involved in the response of sweet potato to salt stress and/or may determine the salt tolerance difference between the two genotypes. In addition, 1,618 differentially expressed regulatory genes were identified, including bZIP, bHLH, ERF, MYB, NAC, and WRKY. Strikingly, transgenic Arabidopsis overexpressing IbNAC7 displayed enhanced salt tolerance compared to WT plants, and higher catalase (CAT) activity, chlorophyll and proline contents, and lower malondialdehyde (MDA) content and reactive oxygen species (ROS) accumulation were detected in transgenic plants compared with that of WT under salt stress. Furthermore, RNA-seq and qRT-PCR analysis displayed that the expression of many stress-related genes was upregulated in transgenic plants. Collectively, these findings provide revealing insights into sweet potato molecular response to salt stress and underlie the complex salt tolerance mechanisms between genotypes, and IbNAC7 was shown as a promising candidate gene to enhance salt tolerance of sweet potato.

SlSTE1 promotes abscisic acid-dependent salt stress-responsive pathways via improving ion homeostasis and reactive oxygen species scavenging in tomato.

High salinity is one of the major limiting factors that reduces crop productivity and quality. Herein, we report that small SALT TOLERANCE ENHANCER1 (STE1) protein without any known conserved domains is required for tomato salt tolerance. Overexpression (OE) of SlSTE1 enhanced the tolerance to multiple chloride salts (NaCl, KCl, and LiCl) and oxidative stress, along with elevated antioxidant enzyme activities, increased abscisic acid (ABA) and chlorophyll contents, and reduced malondialdehyde (MDA) and reactive oxygen species (ROS) accumulations compared to that of wild-type (WT) plants. Moreover, decreased K+ efflux and increased H+ efflux were detected in the OE plants, which induced a higher K+ /Na+ ratio. In contrast, SlSTE1-RNAi plants displayed decreased tolerance to salt stress. RNA-seq data revealed 1 330 differentially expressed genes in the OE plants versus WT plants under salt stress, and the transcription of numerous and diverse genes encoding transcription factors, stress-related proteins, secondary metabolisms, kinases, and hormone synthesis/signaling-related proteins (notably ABA and 1-aminocyclopropane-1-carboxylate) was greatly elevated. Furthermore, SlSTE1-OE plants showed increased sensitivity to ABA, and the results suggest that SlSTE1 promotes ABA-dependent salt stress-responsive pathways by interacting with SlPYLs and SlSnRK2s. Collectively, our findings reveal that the small SlSTE1 protein confers salt tolerance via ABA signaling and ROS scavenging and improves ion homeostasis in tomato.