Ectopic expression of the apple nucleus-encoded thylakoid protein MdY3IP1 triggers early-flowering and enhanced salt-tolerance in Arabidopsis thaliana

Proteome Dynamics Analysis Reveals the Potential Mechanisms of Salinity and Drought Response during Seed Germination and Seedling Growth in Tamarix hispida

Understanding the molecular mechanisms of seed germination and seedling growth is vital for mining functional genes for the improvement of plant drought in a desert. Tamarix hispida is extremely resistant to drought and soil salinity perennial shrubs or trees. This study was the first to investigate the protein abundance profile of the transition process during the processes of T. hispida seed germination and seedling growth using label-free proteomics approaches. Our data suggested that asynchronous regulation of transcriptomics and proteomics occurs upon short-term seed germination and seedling growth of T. hispida. Enrichment analysis revealed that the main differentially abundant proteins had significant enrichment in stimulus response, biosynthesis, and metabolism. Two delta-1-pyrroline-5-carboxylate synthetases (P5CS), one Ycf3-interacting protein (Y3IP), one low-temperature-induced 65 kDa protein-like molecule, and four peroxidases (PRX) were involved in both water deprivation and hyperosmotic salinity responses. Through a comparative analysis of transcriptomics and proteomics, we found that proteomics may be better at studying short-term developmental processes. Our results support the existence of several mechanisms that enhance tolerance to salinity and drought stress during seedling growth in T. hispida.

Transcriptome and Metabolome Analysis Reveals Salt-Tolerance Pathways in the Leaves and Roots of ZM-4 (Malus zumi) in the Early Stages of Salt Stress

The breeding of salt-tolerant rootstock relies heavily on the availability of salt-tolerant Malus germplasm resources. The first step in developing salt-tolerant resources is to learn their molecular and metabolic underpinnings. Hydroponic seedlings of both ZM-4 (salt-tolerant resource) and M9T337 (salt-sensitive rootstock) were treated with a solution of 75 mM salinity. ZM-4's fresh weight increased, then decreased, and then increased again after being treated with NaCl, whereas M9T337's fresh weight continued to decrease. The results of transcriptome and metabolome after 0 h (CK) and 24 h of NaCl treatment showed that the leaves of ZM-4 had a higher content of flavonoids (phloretinm, naringenin-7-O-glucoside, kaempferol-3-O-galactoside, epiafzelechin, etc.) and the genes (CHI, CYP, FLS, LAR, and ANR) related to the flavonoid synthesis pathway showed up-regulation, suggesting a high antioxidant capacity. In addition to the high polyphenol content (L-phenylalanine, 5-O-p-coumaroyl quinic acid) and the high related gene expression (4CLL9 and SAT), the roots of ZM-4 exhibited a high osmotic adjustment ability. Under normal growing conditions, the roots of ZM-4 contained a higher content of some amino acids (L-proline, tran-4-hydroxy-L-prolin, L-glutamine, etc.) and sugars (D-fructose 6-phosphate, D-glucose 6-phosphate, etc.), and the genes (GLT1, BAM7, INV1, etc.) related to these two pathways were highly expressed. Furthermore, some amino acids (S-(methyl) glutathione, N-methyl-trans-4-hydroxy-L-proline, etc.) and sugars (D-sucrose, maltotriose, etc.) increased and genes (ALD1, BCAT1, AMY1.1, etc.) related to the pathways showed up-regulation under salt stress. This research provided theoretical support for the application of breeding salt-tolerant rootstocks by elucidating the molecular and metabolic mechanisms of salt tolerance during the early stages of salt treatment for ZM-4.

Yang cycle enzyme DEP1: its moonlighting functions in PSI and ROS production during leaf senescence

Ethylene-mediated leaf senescence and the compromise of photosynthesis are closely associated but the underlying molecular mechanism is a mystery. Here we reported that apple DEHYDRATASE-ENOLASE-PHOSPHATASE-COMPLEX1 (MdDEP1), initially characterized to its enzymatic function in the recycling of the ethylene precursor SAM, plays a role in the regulation of photosystem I (PSI) activity, activating reactive oxygen species (ROS) homeostasis, and negatively regulating the leaf senescence. A series of Y2H, Pull-down, CO-IP and Cell-free degradation biochemical assays showed that MdDEP1 directly interacts with and dephosphorylates the nucleus-encoded thylakoid protein MdY3IP1, leading to the destabilization of MdY3IP1, reduction of the PSI activity, and the overproduction of ROS in plant cells. These findings elucidate a novel mechanism that the two pathways intersect at MdDEP1 due to its moonlighting role in destabilizing MdY3IP1, and synchronize ethylene-mediated leaf senescence and the compromise of photosynthesis.

A Review of Recent Advances and Future Directions in the Management of Salinity Stress in Finger Millet

Salinity stress is a major environmental impediment affecting the growth and production of crops. Finger millet is an important cereal grown in many arid and semi-arid areas of the world characterized by erratic rainfall and scarcity of good-quality water. Finger millet salinity stress is caused by the accumulation of soluble salts due to irrigation without a proper drainage system, coupled with the underlying rocks having a high salt content, which leads to the salinization of arable land. This problem is projected to be exacerbated by climate change. The use of new and efficient strategies that provide stable salinity tolerance across a wide range of environments can guarantee sustainable production of finger millet in the future. In this review, we analyze the strategies that have been used for salinity stress management in finger millet production and discuss potential future directions toward the development of salt-tolerant finger millet varieties. This review also describes how advanced biotechnological tools are being used to develop salt-tolerant plants. The biotechnological techniques discussed in this review are simple to implement, have design flexibility, low cost, and highly efficient. This information provides insights into enhancing finger millet salinity tolerance and improving production.

MdCER2 conferred to wax accumulation and increased drought tolerance in plants

Drought can activate many stress responses in plant growth and development, including the synthesis of epidermal wax and the induction of abscisic acid (ABA), and increased wax accumulation will improve plant drought resistance. Therefore, an examination of wax biosynthesis genes could help to better understand the molecular mechanism of environmental factors regulating wax biosynthesis and the wax associated stress response. Here, we identified the MdCER2 gene from the 'Gala' (Malus× domestica Borkh.) variety of domestic apple, which is a homolog of Arabidopsis AtCER2. It possesses a transferase domain and the protein localizes on the cell membrane. The MdCER2 gene was constitutively expressed in apple tissues and was induced by drought treatment. Finally, we transformed the MdCER2 gene into Arabidopsis to identify its function, and found ectopic expression of MdCER2 promoted accumulation of cuticular wax in both leaves and stems, decreased water loss and permeability in leaves, increased lateral root number, changed plant ABA sensitivity, and increased drought resistance.

A genome-wide identification, characterization and functional analysis of salt-related long non-coding RNAs in non-model plant Pistacia vera L. using transcriptome high throughput sequencing

Long non-coding RNAs (lncRNAs) play crucial roles in regulating gene expression in response to plant stresses. Given the importance regulatory roles of lncRNAs, providing methods for predicting the function of these molecules, especially in non-model plants, is strongly demanded by researchers. Here, we constructed a reference sequence for lncRNAs in P. vera (Pistacia vera L.) with 53220 transcripts. In total, we identified 1909 and 2802 salt responsive lncRNAs in Ghazvini, a salt tolerant cultivar, after 6 and 24 h salt treatment, respectively and 1820 lncRNAs in Sarakhs, a salt sensitive cultivar, after 6 h salt treatment. Functional analysis of these lncRNAs by several hybrid methods, revealed that salt responsive NAT-related lncRNAs associated with transcription factors, CERK1, LEA, Laccase genes and several genes involved in the hormone signaling pathways. Moreover, gene ontology (GO) enrichment analysis of salt responsive target genes related to top five selected lncRNAs showed their involvement in the regulation of ATPase, cation transporter, kinase and UDP-glycosyltransferases genes. Quantitative real-time PCR (qRT-PCR) experiment results of lncRNAs, pre-miRNAs and mature miRNAs were in accordance with our RNA-seq analysis. In the present study, a comparative analysis of differentially expressed lncRNAs and microRNA precursors between salt tolerant and sensitive pistachio cultivars provides valuable knowledge on gene expression regulation under salt stress condition.

The BpMYB4 Transcription Factor From Betula platyphylla Contributes Toward Abiotic Stress Resistance and Secondary Cell Wall Biosynthesis

The MYB (v-myb avian myeloblastosis viral oncogene homolog) family is one of the largest transcription factor families in plants, and is widely involved in the regulation of plant metabolism. In this study, we show that a MYB4 transcription factor, BpMYB4, identified from birch (Betula platyphylla Suk.) and homologous to EgMYB1 from Eucalyptus robusta Smith and ZmMYB31 from Zea mays L. is involved in secondary cell wall synthesis. The expression level of BpMYB4 was higher in flowers relative to other tissues, and was induced by artificial bending and gravitational stimuli in developing xylem tissues. The expression of this gene was not enriched in the developing xylem during the active season, and showed higher transcript levels in xylem tissues around sprouting and near the dormant period. BpMYB4 also was induced express by abiotic stress. Functional analysis indicated that expression of BpMYB4 in transgenic Arabidopsis (Arabidopsis thaliana) plants could promote the growth of stems, and result in increased number of inflorescence stems and shoots. Anatomical observation of stem sections showed lower lignin deposition, and a chemical contents test also demonstrated increased cellulose and decreased lignin content in the transgenic plants. In addition, treatment with 100 mM NaCl and 200 mM mannitol resulted in the germination rate of the over-expressed lines being higher than that of the wild-type seeds. The proline content in transgenic plants was higher than that in WT, but MDA content was lower than that in WT. Further investigation in birch using transient transformation techniques indicated that overexpression of BpMYB4 could scavenge hydrogen peroxide and O₂ ^.- and reduce cell damage, compared with the wild-type plants. Therefore, we believe that BpMYB4 promotes stem development and cellulose biosynthesis as an inhibitor of lignin biosynthesis, and has a function in abiotic stress resistance.

The walnut transcription factor JrGRAS2 contributes to high temperature stress tolerance involving in Dof transcriptional regulation and HSP protein expression

BACKGROUND

GRAS transcription factor (TF) family is unique and numerous in higher plants with diverse functions that involving in plant growth and development processes, such as gibberellin (GA) signal transduction, root development, root nodule formation, and mycorrhiza formation. Walnut tree is exposed to various environmental stimulus that causing concern about its resistance mechanism. In order to understand the molecular mechanism of walnut to adversity response, a GRAS TF (JrGRAS2) was cloned and characterized from Juglans regia in this study.

RESULTS

A 1500 bp promoter fragment of JrGRAS2 was identified from the genome of J. regia, in which the cis-elements were screened. This JrGRAS2 promoter displayed expression activity that was enhanced significantly by high temperature (HT) stress. Yeast one-hybrid assay, transient expression and chromatin immunoprecipitation (Chip)-PCR analysis revealed that JrDof3 could specifically bind to the DOFCOREZM motif and share similar expression patterns with JrGRAS2 under HT stress. The transcription of JrGRAS2 was induced by HT stress and up-regulated to 6.73-~11.96-fold in the leaf and 2.53-~4.50-fold in the root to control, respectively. JrGRAS2 was overexpressed in Arabidopsis, three lines with much high expression level of JrGRAS2 (S3, S7, and S8) were selected for HT stress tolerance analysis. Compared to the wild type (WT) Arabidopsis, S3, S7, and S8 exhibited enhanced seed germination rate, fresh weight accumulation, and activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione-S-transferase (GST) under HT stress. In contrast, the Evans blue staining, electrolyte leakage (EL) rates, hydrogen dioxide (H₂O₂) and malondialdehyde (MDA) content of transgenic seedlings were all lower than those of WT exposed to HT stress. Furthermore, the expression of heat shock proteins (HSPs) in S3, S7, and S8 was significant higher than those in WT plants. The similar results were obtained in JrGRAS2 transient overexpression walnut lines under normal and HT stress conditions.

CONCLUSIONS

Our results suggested that JrDof3 TF contributes to improve the HT stress response of JrGRAS2, which could effectively control the expression of HSPs to enhance HT stress tolerance. JrGRAS2 is an useful candidate gene for heat response in plant molecular breeding.