Overexpression of the CaHB12 transcription factor in cotton (Gossypium hirsutum) improves drought tolerance

Improvement of qualitative and quantitative traits in cotton under normal and stressed environments using genomics and biotechnological tools: A review

Due to the increasing demand for high-quality and high fiber-yielding cotton (Gossypium spp.), research into the development of stress-resilient cotton cultivars has acquired greater significance. Various biotic and abiotic stressors greatly affect cotton production and productivity, posing challenges to the future of the textile industry. Moreover, the content and quality of cottonseed oil can also potentially be influenced by future environmental conditions. Apart from conventional methods, genetic engineering has emerged as a potential tool to improve cotton fiber quality and productivity. Identification and modification of genome sequences and the expression levels of yield-related genes using genetic engineering approaches have enabled to increase both the quality and yields of cotton fiber and cottonseed oil. Herein, we evaluate the significance and molecular mechanisms associated with the regulation of cotton agronomic traits under both normal and stressful environmental conditions. In addition, the importance of gossypol, a toxic phenolic compound in cottonseed that can limit consumption by animals and humans, is reviewed and discussed.

Genome-Wide Identification of the GhANN Gene Family and Functional Validation of GhANN11 and GhANN4 under Abiotic Stress

Annexins (ANNs) are a structurally conserved protein family present in almost all plants. In the present study, 27 GhANNs were identified in cotton and were unevenly distributed across 14 chromosomes. Transcriptome data and RT-qPCR results revealed that multiple GhANNs respond to at least two abiotic stresses. Similarly, the expression levels of GhANN4 and GhANN11 were significantly upregulated under heat, cold, and drought stress. Using virus-induced gene silencing (VIGS), functional characterization of GhANN4 and GhANN11 revealed that, compared with those of the controls, the leaf wilting of GhANN4-silenced plants was more obvious, and the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were lower under NaCl and PEG stress. Moreover, the expression of stress marker genes (GhCBL3, GhDREB2A, GhDREB2C, GhPP2C, GhRD20-2, GhCIPK6, GhNHX1, GhRD20-1, GhSOS1, GhSOS2 and GhSnRK2.6) was significantly downregulated in GhANN4-silenced plants after stress. Under cold stress, the growth of the GHANN11-silenced plants was significantly weaker than that of the control plants, and the activities of POD, SOD, and CAT were also lower. However, compared with those of the control, the elasticity and orthostatic activity of the GhANN11-silenced plants were greater; the POD, SOD, and CAT activities were higher; and the GhDREB2C, GhHSP, and GhSOS2 expression levels were greater under heat stress. These results suggest that different GhANN family members respond differently to different types of abiotic stress.

Enhancing cold and drought tolerance in cotton: a protective role of SikCOR413PM1

The present study explored the potential role of cold-regulated plasma membrane protein COR413PM1 isolated from Saussurea involucrata (Matsum. & Koidz)(SikCOR413PM1), in enhancing cotton (Gossypium hirsutum) tolerance to cold and drought stresses through transgenic methods. Under cold and drought stresses, the survival rate and the fresh and dry weights of the SikCOR413PM1-overexpressing lines were higher than those of the wild-type plants, and the degree of leaf withering was much lower. Besides, overexpressing SikCOR413PM1 overexpression increased the relative water content, reduced malondialdehyde content and relative conductivity, and elevated proline and soluble sugar levels in cotton seedlings. These findings suggest that SikCOR413PM1 minimizes cell membrane damage and boosts plant stability under challenging conditions. Additionally, overexpression of this gene upregulated antioxidant enzyme-related genes in cotton seedlings, resulting in enhanced antioxidant enzyme activity, lowered peroxide content, and reduced oxidative stress. SikCOR413PM1 overexpression also modulated the expression of stress-related genes (GhDREB1A, GhDREB1B, GhDREB1C, GhERF2, GhNAC3, and GhRD22). In field trials, the transgenic cotton plants overexpressing SikCOR413PM1 displayed high yields and increased environmental tolerance. Our study thus demonstrates the role of SikCOR413PM1 in regulating stress-related genes, osmotic adjustment factors, and peroxide content while preserving cell membrane stability and improving cold and drought tolerance in cotton.

A multiomics integrative analysis of color de-synchronization with softening of 'Hass' avocado fruit: A first insight into a complex physiological disorder

Exocarp color de-synchronization with softening of 'Hass' avocado is a relevant recurrent problem for the avocado supply chain. This study aimed to unravel the mechanisms driving this de-synchronization integrating omics datasets from avocado exocarp of different storage conditions and color phenotypes. In addition, we propose potential biomarkers to predict color synchronized/de-synchronized fruit. Integration of transcriptomics, proteomics and metabolomics and network analysis revealed eight transcription factors associated with differentially regulated genes between regular air (RA) and controlled atmosphere (CA) and twelve transcription factors related to avocado fruit color de-synchronization control in ready-to-eat stage. CA was positively correlated to auxins, ethylene, cytokinins and brassinosteroids-related genes, while RA was characterized by enrichment of cell wall remodeling and abscisic acid content associated genes. At ready-to-eat higher contents of flavonoids, abscisic acid and brassinosteroids were associated with color-softening synchronized avocados. In contrast, de-synchronized fruit revealed increases of jasmonic acid, salicylic acid and auxin levels.

Overexpression of Pyrus sinkiangensis HAT5 enhances drought and salt tolerance, and low-temperature sensitivity in transgenic tomato

The homeodomain-leucine zipper protein HAT belongs to the homeodomain leucine zipper subfamily (HD-Zip) and is important for regulating plant growth and development and stress tolerance. To investigate the role of HAT5 in tolerance to drought, salt, and low temperature stress, we selected a HAT gene from Pyrus sinkiangensis Yü (Pyrus sinkiangensis T.T. Yu). The sequences were analyzed using ioinformatics, and the overexpressed tomato lines were obtained using molecular biology techniques. The phenotypes, physiological, and biochemical indexes of the wild-type and transgenic tomato lines were observed under different stress conditions. We found that the gene had the highest homology with PbrHAT5. Under drought and NaCl stress, osmotic regulatory substances (especially proline) were significantly accumulated, and antioxidant enzyme activities were enhanced. The malondialdehyde level and relative electrical conductivity of transgenic tomatoes under low temperature (freezing) stress were significantly higher than those of wild-type tomatoes. The reactive oxygen species scavenging system was unbalanced. This study found that PsHAT5 improved the tolerance of tomatoes to drought and salt stress by regulating proline metabolism and oxidative stress ability, reducing the production of reactive oxygen species, and maintaining normal cell metabolism. In conclusion, the PsHAT5 transcription factor has great potential in crop resistance breeding, which lays a theoretical foundation for future excavation of effective resistance genes of the HD-Zip family and experimental field studies.

Genetic manipulation for abiotic stress resistance traits in crops

Abiotic stresses are major limiting factors that pose severe threats to agricultural production. Conventional breeding has significantly improved crop productivity in the last century, but traditional breeding has reached its maximum capacity due to the multigenic nature of abiotic stresses. Alternatively, biotechnological approaches could provide new opportunities for producing crops that can adapt to the fast-changing environment and still produce high yields under severe environmental stress conditions. Many stress-related genes have been identified and manipulated to generate stress-tolerant plants in the past decades, which could lead to further increase in food production in most countries of the world. This review focuses on the recent progress in using transgenic technology and gene editing technology to improve abiotic stress tolerance in plants, and highlights the potential of using genetic engineering to secure food and fiber supply in a world with an increasing population yet decreasing land and water availability for food production and fast-changing climate that will be largely hostile to agriculture.

Identification and characterization of stress responsive homeodomain leucine zipper transcription factors in Medicago truncatula

BACKGROUND

Homeodomain leucine zipper (HD-ZIP) transcription factors play roles in regulating plant development and responses to abiotic stresses; however, how HD-ZIP genes in Medicago truncatula are involved in abiotic stress response remains elusive.

METHODS AND RESULTS

The HD-ZIP I genes in Medicago truncatula were identified and characterized, and their expression patterns in different tissues and under different abiotic stresses were analyzed. A total of 15 Medicago truncatula HD-ZIP I genes were identified and a phylogenetic analysis of HD-ZIP I proteins in Arabidopsis thaliana and Medicago truncatula was conducted. Fifteen HD-ZIP I genes showed diverse tissue preferences. Among them, expressions of MtHB22 and MtHB51 were specially detected in vegetative buds. In addition, they responded to various abiotic stresses, including salinity and osmotic stress and abscisic acid (ABA). For instance, MtHB7 and MtHB12 expression levels were found to be positively associated with salt, osmotic stress and ABA in both shoots and roots, while MtHB13 and MtHB23 were negatively associated with these stresses in Medicago truncatula.

CONCLUSION

The HD-ZIP I genes in Medicago truncatula are evolutionarily conserved, but also exhibit gene duplication and gene loss events. Differential expression analysis of Medicago truncatula HD-ZIP I genes indicated their crucial roles in abiotic stress responses. Our genome-wide analysis of the HD-ZIP I transcription factor family in Medicago truncatula provided a valuable reference for further research.

Improved cotton transformation protocol mediated by Agrobacterium and biolistic combined-methods

The combined Agrobacterium- and biolistic-mediated methods of cotton transformation provide a straightforward and highly efficient protocol for obtaining transgenic cotton. Cotton (Gossypium spp.) is the most important crop for natural textile fiber production worldwide. Nonetheless, one of the main challenges in cotton production are the losses resulting from insect pests, pathogens, and abiotic stresses. One effective way to solve these issues is to use genetically modified (GM) varieties. Herein, we describe an improved protocol for straightforward and cost-effective genetic transformation of cotton embryo axes, merging biolistics and Agrobacterium. The experimental steps include (1) Agrobacterium preparation, (2) seed sterilization, (3) cotton embryo excision, (4) lesion of shoot-cells by tungsten bombardment, (5) Agrobacterium-mediated transformation, (6) embryo co-culture, (7) regeneration and selection of transgenic plants in vitro, and (8) molecular characterization of plants. Due to the high regenerative power of the embryonic axis and the exceptional ability of the meristem cells for plant regeneration through organogenesis in vitro, this protocol can be performed in approximately 4-10 weeks, with an average plant regeneration of about 5.5% (± 0.53) and final average transformation efficiency of 60% (± 0.55). The transgene was stably inherited, and most transgenic plants hold a single copy of the transgene, as desirable and expected in Agrobacterium-mediated transformation. Additionally, the transgene was stably expressed over generations, and transgenic proteins could be detected at high levels in the T₂ generation of GM cotton plants. The T₂ progeny showed no phenotypic or productivity disparity compared to wild-type plants. Collectively, the use of cotton embryo axes and the enhanced DNA-delivery system by combining particle bombardment and Agrobacterium infection enabled efficient transgenic plant recovery, overcoming usual limitations associated with the recalcitrance of several cotton genotypes subjected to somatic embryogenesis. The improved approach states this method's success for cotton genetic modification, allowing us to obtain GM cotton plants carrying traits, which are of fundamental relevance for the advancement of global agribusiness.