Rapid Identification of Pollen- and Anther-Specific Genes in Response to High-Temperature Stress Based on Transcriptome Profiling Analysis in Cotton

Unraveling the genetic and molecular basis of heat stress in cotton

Human activities and climate change have resulted in frequent and intense weather fluctuations, leading to diverse abiotic stresses on crops which hampers greatly their metabolic activities. Heat stress, a prevalent abiotic factor, significantly influences cotton plant biological activities resulting in reducing yield and production. We must deepen our understanding of how plants respond to heat stress across various dimensions, encompassing genes, RNAs, proteins, metabolites for effective cotton breeding. Multi-omics methods, primarily genomics, transcriptomics, proteomics, metabolomics, and phenomics, proves instrumental in studying cotton's responses to abiotic stresses. Integrating genomics, transcriptomics, proteomics, and metabolomic is imperative for our better understanding regarding genetics and molecular basis of heat tolerance in cotton. The current review explores fundamental omics techniques, covering genomics, transcriptomics, proteomics, and metabolomics, to highlight the progress made in cotton omics research.

A multi-organ maize metabolic model connects temperature stress with energy production and reducing power generation

Climate change has adversely affected maize productivity. Thereby, a holistic understanding of metabolic crosstalk among its organs is important to address this issue. Thus, we reconstructed the first multi-organ maize metabolic model, iZMA6517, and contextualized it with heat and cold stress transcriptomics data using expression distributed reaction flux measurement (EXTREAM) algorithm. Furthermore, implementing metabolic bottleneck analysis on contextualized models revealed differences between these stresses. While both stresses had reducing power bottlenecks, heat stress had additional energy generation bottlenecks. We also performed thermodynamic driving force analysis, revealing thermodynamics-reducing power-energy generation axis dictating the nature of temperature stress responses. Thus, a temperature-tolerant maize ideotype can be engineered by leveraging the proposed thermodynamics-reducing power-energy generation axis. We experimentally inoculated maize root with a beneficial mycorrhizal fungus, Rhizophagus irregularis, and as a proof-of-concept demonstrated its efficacy in alleviating temperature stress. Overall, this study will guide the engineering effort of temperature stress-tolerant maize ideotypes.

High-temperature stress in crops: male sterility, yield loss and potential remedy approaches

Global food security is one of the utmost essential challenges in the 21st century in providing enough food for the growing population while coping with the already stressed environment. High temperature (HT) is one of the main factors affecting plant growth, development and reproduction and causes male sterility in plants. In male reproductive tissues, metabolic changes induced by HT involve carbohydrates, lipids, hormones, epigenetics and reactive oxygen species, leading to male sterility and ultimately reducing yield. Understanding the mechanism and genes involved in these pathways during the HT stress response will provide a new path to improve crops by using molecular breeding and biotechnological approaches. Moreover, this review provides insight into male sterility and integrates this with suggested strategies to enhance crop tolerance under HT stress conditions at the reproductive stage.

Pollen-Pistil Interaction

The aim of this Special Issue is to highlight the molecular dialogue between the pollen tube and the pistil [...].

A male-sterile mutant with necrosis-like dark spots on anthers was generated in cotton

Although conventional hybrid breeding has paved the way for improving cotton production and other properties, it is undoubtedly time and labor consuming, while the cultivation of male sterile line can fix the problem. Here, we induced male sterile mutants by simultaneously editing three cotton EXCESS MICROSPOROCYTES1 (GhEMS1) genes by CRISPR/Cas9. Notably, the GhEMS1 genes are homologous to AtEMS1 genes, which inhibit the production of middle layer and tapetum cells as well, leading to male sterility in cotton. Interestingly, there are necrosis-like dark spots on the surface of the anthers of GhEMS1s mutants, which is different from AtEMS1 mutant whose anther surface is clean and smooth, suggesting that the function of EMS1 gene has not been uncovered yet. Moreover, we have detected mutations in GhEMS1 genes from T₀ to T₃ mutant plants, which had necrosis-like dark spots as well, indicating that the mutation of the three GhEMS1 genes could be stably inherited. Dynamic transcriptomes showed plant hormone pathway and anther development genetic network were differential expression in mutant and wild-type anthers. And the lower level of IAA content in the mutant anthers than that in the wild type at four anther developmental stages may be the reason for the male sterility. This study not only facilitates the exploration of the basic research of cotton male sterile lines, but also provides germplasms for accelerating the hybrid breeding in cotton.

Responses of differential metabolites and pathways to high temperature in cucumber anther

Cucumber is one of the most important vegetable crops, which is widely planted all over the world. Cucumber always suffers from high-temperature stress in South China in summer. In this study, liquid chromatography-mass spectrometry (LC-MS) analysis was used to study the differential metabolites of cucumber anther between high-temperature (HT) stress and normal condition (CK). After HT, the pollen fertility was significantly reduced, and abnormal anther structures were observed by the paraffin section. In addition, the metabolomics analysis results showed that a total of 125 differential metabolites were identified after HT, consisting of 99 significantly upregulated and 26 significantly downregulated metabolites. Among these differential metabolites, a total of 26 related metabolic pathways were found, and four pathways showed significant differences, namely, porphyrin and chlorophyll metabolism; plant hormone signal transduction; amino sugar and nucleotide sugar metabolism; and glycine, serine, and threonine metabolism. In addition, pollen fertility was decreased by altering the metabolites of plant hormone signal transduction and amino acid and sugar metabolism pathway under HT. These results provide a comprehensive understanding of the metabolic changes in cucumber anther under HT.

Response of root and root hair phenotypes of cotton seedlings under high temperature revealed with RhizoPot

Driven by the increase in its frequency and duration, high temperature weather is increasingly seriously affecting crop development. High temperature inhibits the leaf development, flowering, and pollination of cotton, but its effects on the roots and root hair phenotypes and lifespans remain unclear. Thus, this study selected the two cotton varieties Nongda 601 (ND) and Guoxin 9 (GX) as materials and adopted the RhizoPot, an in situ root observation system, to investigate the effects of high temperature (38°C day and 32°C night) on the growth dynamics of the aboveground parts and root phenotypes of cotton at the seedling stage. The results showed that high temperature reduced the net photosynthetic rate and chlorophyll content, decreased the dry matter accumulation and transfer to the root, and lowered the root-shoot ratio (R/S ratio). The root phenotypes changed significantly under high temperature. After 7 d of high temperature stress, the root lengths of ND and GX decreased by 78.14 mm and 59.64 mm, respectively. Their specific root lengths increased by 79.60% and 66.11%, respectively. Their specific root surface areas increased by 418.70 cm²·g^-1 and 433.42 cm²·g^-1, respectively. Their proportions of very fine roots increased to 99.26% and 97.16%, respectively. After the removal of high temperature (RHT), their root lengths tended to increase, and their proportions of very fine roots continued to increase. The root hairs of ND and GX were also significantly affected by high temperature. In particular, the root hair densities of ND and GX decreased by 52.53% and 56.25%, respectively. Their average root hair lengths decreased by 96.62% and 74.29%, respectively. Their root hair lifespans decreased by 7 d and 10 d, respectively. After the RHT, their average root hair lengths failed to recover. A principal component analysis indicated that the root architectures were significantly affected by root hair density, average root hair length, specific root length, and specific root surface area under high temperatures. In summary, cotton adapts to high temperature environments by increasing the specific root length, specific root surface area, and the proportions of very fine roots, and reducing the lifespan of root hairs.