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Additional file 1: Fig S1. Limonene producing gene modules. Fig S2. Monoterpene profile of engineered Rhodosporidium toruloides Np11. Fig S3. Characterization of the Limonene Configuration. Fig S4. The limonene synthases utilized in R. toruloides. Fig S5. Effect of fermentation system on limonene production. Fig S6. Effects of dodecane overlay on limonene production with engineered R. toruloides strains. Fig S7. Comparison of limonene production of engineered R. toruloides strains in shake flasks. Fig S8. Limonene tolerance of R. toruloides. Fig S9. The influence of working volume on limonene production in shake flasks.

The C4 plants like maize are at an advantage because they exhibit higher carbon conversion efficiency than C3 during photosynthesis. Using the evaluation of photosynthetic phenotypes and subcellular structure, and high-quality transcriptome analysis for four types of leaves from a bundle sheath defective maize mutant (bsd) and 501 wild line, the key target genes, important transcription factors, and specific pathways were obtained, which may regulate the C-concentrating mechanisms and antioxidant protection of the photosynthetic system, gibberellin signaling, ribosome editing, glycolysis, and chlorophyll biosynthesis. Based on these target genes, a novel network with photosynthetic transformation efficiency with oxidative decarboxylation and ribosome regulation was filtered innovatively by Cytoscape, which adds to our understanding for high-efficiency C-fixation and its genetic improvement in C3 and C4 plants.

Background Sodium toxicity and potassium insufficient are important factors affecting the growth and development of maize in saline soil. The monovalent cation proton antiporter (CPA) superfamily comprises Na + /H + exchanger (NHX), K + efflux antiporter (KEA), and cation/H + exchanger (CHX) subfamily proteins, which play vital functions in maize salt tolerance. Results A total of 35 ZmCPA genes were identified in maize, and they were phylogenetically classified into 13 ZmNHXs , 16 ZmCHXs and 6 ZmKEAs . ZmCPA genes have a conserved gene structure, with the determined introns range from 11 to 25, 0 to 5 and 16 to 19 in ZmNHXs, ZmCHXs, ZmKEAs , respectively. All proteins have transmembrane domains, with an average transmembrane number of 8, 10, and 10 in ZmNHX, ZmCHX and ZmKEA proteins, respectively. Transient expression in maize protoplasts showed that ZmCHX16 and ZmNHX8 are located in the cell membrane. All ZmCHX subfamily genes showed lower expression compared to ZmNHX and ZmKEA subfamilies. Diverse expression in the 60 tissues and modulated expression in response to salt stress suggested ZmCPAs’ role in maize development and salt stress. Yeast complementary experiment revealed the function of ZmNHX8 , ZmCHX8 , - 12 , - 14 , - 16 and ZmKEA6 in salt tolerance. Maize mutants zmnhx8 and zmkea6 further validated the important function of ZmNHX8 and ZmKEA6 in salt tolerance. Phosphorylation sites and cis -acting regulation elements analyses indicated that phosphorylation and transcriptional regulation may be involved in salt tolerance of ZmCPA genes. Conclusions Our study provides comprehensive information about ZmCPA gene superfamily, which would be useful in their future functional characterization.

Drought stress is a major abiotic factor compromising plant cell physiological and molecular events, consequently limiting crop growth and productivity. Maize (Zea mays L.) is among the most drought-susceptible food crops. Therefore, understanding the mechanisms underlying drought-stress responses remains critical for crop improvement. To decipher the molecular mechanisms underpinning maize drought tolerance, here, we used a comparative morpho-physiological and proteomics analysis approach to monitor the changes in germinating seeds of two incongruent (drought-sensitive wild-type Vp16 and drought-tolerant mutant vp16) lines exposed to polyethylene-glycol-induced drought stress for seven days. Our physiological analysis showed that the tolerant line mutant vp16 exhibited better osmotic stress endurance owing to its improved reactive oxygen species scavenging competency and robust osmotic adjustment as a result of greater cell water retention and enhanced cell membrane stability. Proteomics analysis identified a total of 1200 proteins to be differentially accumulated under drought stress. These identified proteins were mainly involved in carbohydrate and energy metabolism, histone H2A-mediated epigenetic regulation, protein synthesis, signal transduction, redox homeostasis and stress-response processes, with carbon metabolism, pentose phosphate and glutathione metabolism pathways being prominent under stress conditions. Interestingly, significant congruence (R2 = 81.5%) between protein and transcript levels was observed by qRT-PCR validation experiments. Finally, we propose a hypothetical model for maize germinating-seed drought tolerance based on our key findings identified herein. Overall, our study offers insights into the overall mechanisms underpinning drought-stress tolerance and provides essential leads into further functional validation of the identified drought-responsive proteins in maize.