A small RNA of miR2119b from soybean CMS line acts as a negative regulator of male fertility in transgenic Arabidopsis

A small heat shock protein GmHSP18.5a improves the male fertility restorability of cytoplasmic male sterility-based restorer line under high temperature stress in soybean

Small heat shock protein (sHSP) is involved in high temperature (HT) stress response. However, the function of sHSPs in regulating male fertility of soybean under HT stress remains largely unknown. Here, we identified a sHSP gene, GmHSP18.5a, which was responded to HT stress during flowering in cytoplasmic male sterility (CMS)-based restorer line of soybean. Moreover, GmHSFA6b turned out to directly activated the expression of GmHSP18.5a by binding to the heat shock cis-element in its promoter. Overexpression of GmHSP18.5a increased male fertility in transgenic Arabidopsis, soybean CMS-based restorer line and its hybrid F1 with CMS line under HT stress. Reactive oxygen species (ROS) content detection revealed that GmHSP18.5a promoted the ROS scavenging ability of Arabidopsis inflorescence and soybean flower bud under HT stress. Enzyme activity assay and gene expression analysis indicated that GmHS18.5a mainly increased the activity of antioxidant enzymes and the expression level of ROS metabolism-related genes under HT stress. Our results indicated that GmHSP18.5a improved the male fertility restorability of CMS-based restorer line in soybean by regulating ROS metabolic pathway and reducing ROS accumulation. Our findings not only revealed the molecular mechanism of sHSP regulating the male fertility of soybean under HT stress, but also provided a theoretical basis for creating strong restorer line with thermotolerance.

ROS accumulation-induced tapetal PCD timing changes leads to microspore abortion in cotton CMS lines

BACKGROUND

Cytoplasmic male sterility (CMS) is the basis of heterosis exploitation. CMS has been used to hybrid production in cotton, but its molecular mechanism remains unclear. CMS is associated with advanced or delayed tapetal programmed cell death (PCD), and reactive oxygen species (ROS) may mediate this process. In this study, we obtained Jin A and Yamian A, two CMS lines with different cytoplasmic sources.

RESULTS

Compared with maintainer Jin B, Jin A anthers showed advanced tapetal PCD with DNA fragmentation, producing excessive ROS which accumulated around the cell membrane, intercellular space and mitochondrial membrane. The activities of peroxidase (POD) and catalase (CAT) enzymes which can scavenge ROS were significantly decreased. However, Yamian A tapetal PCD was delayed with lower ROS content, and the activities of superoxide dismutase (SOD) and POD were higher than its maintainer. These differences in ROS scavenging enzyme activities may be caused by isoenzyme gene expressions. In addition, we found the excess ROS generated in Jin A mitochondria and ROS overflow from complex III might be the source in parallel with the reduction of ATP content.

CONCLUSION

ROS accumulation or abrogation were mainly caused by the joint action of ROS generation and scavenging enzyme activities transformation, which led to the abnormal progression of tapetal PCD, affected the development of microspores, and eventually contributed to male sterility. In Jin A, tapetal PCD in advance might be caused by mitochondrial ROS overproduction, accompanied by energy deficiency. The above studies will provide new insights into the cotton CMS and guide the follow-up research ideas.

The miR156b-GmSPL2b module mediates male fertility regulation of cytoplasmic male sterility-based restorer line under high-temperature stress in soybean

High-temperature (HT) stress at flowering stage causes significant damage to soybean, including pollen abortion and fertilization failure, but few genes involved in male fertility regulation under HT stress in soybean have been characterized. Here, we demonstrated that miR156b-GmSPL2b module involved in male fertility regulation of soybean cytoplasmic male sterility (CMS)-based restorer line under HT stress. Overexpression of miR156b decreased male fertility in soybean CMS-based restorer line and its hybrid F₁ with CMS line under HT stress. RNA-seq analysis found that miR156b mediated male fertility regulation in soybean under HT stress by regulating the expression of pollen development and HT response related genes. Metabolomic analysis of miR156bOE revealed reduction in flavonoid content under HT stress. Integrated transcriptomic and metabolomic analysis showed that the overexpression of miR156b caused flavonoid metabolism disorder in soybean flower bud under HT stress. Knockout of GmSPL2b also decreased the thermotolerance of soybean CMS-based restorer line during flowering. Moreover, GmSPL2b turned out to be directly bounded to the promoter of GmHSFA6b. Further verification indicated that GmHSFA6b overexpression enhanced HT tolerance in Arabidopsis during flowering. Substance content and gene expression analysis revealed that miR156b-GmSPL2b may mediate reactive oxygen species clearance by regulating flavonoid metabolism, thus participating in the regulation of male fertility in soybean under HT stress. This study not only provided important progress for understanding the molecular mechanism of miR156b-GmSPL2b regulating the male fertility of soybean CMS-based restorer line under HT stress, but also provided genetic resources and theoretical basis for creating HT-tolerant strong restorer lines.

Promoter Cis-Element Analyses Reveal the Function of αVPE in Drought Stress Response of Arabidopsis

Vacuolar processing enzyme (VPE) is a cysteine protease responsible for vacuolar proteins’ maturation and regulation of programmed cell death (PCD). Four isoforms of Arabidopsis thaliana VPEs were identified previously, but only the functions of βVPE, γVPE, and δVPE were determined. The specific function of a gene is linked to the cis-acting elements in the promoter region. A promoter analysis found repetitive drought-related cis-elements in αVPE, which highlight its potential involvement in drought regulation in A. thaliana. The further co-expression network portraying genes interacting with αVPE substantiated its drought-regulation-related function. Expression of αVPE was upregulated after drought treatment in A. thaliana. To confirm the role of αVPE, a loss of function study revealed that αVPE knockout mutants remained green compared with WT after drought treatment. The mutants had reduced proline activity, decreased sucrose content, and lower MDA content, but increased photosynthetic pigments, indicating that αVPE negatively regulates drought tolerance in A. thaliana. Taken together, our findings serve as important evidence of the involvement of αVPE in modulating drought tolerance in A. thaliana.

The transcription factor TaGAMYB modulates tapetum and pollen development of TGMS wheat YanZhan 4110S via the gibberellin signaling

Male reproductive development in higher plants experienced a series of complex biological processes, which can be regulated by Gibberellins (GA). The transcriptional factor GAMYB is a crucial component of GA signaling in anther development. However, the mechanism of GAMYB in wheat male reproduction is less understood. Here, we found that the thermo-sensitive genic male sterilitywheat line YanZhan 4110S displayed delayed tapetum programmed cell death and pollen abortive under the hot temperature stress. Combined with RNA-Sequencing data analysis, TaGAMYB associated with fertility conversion was isolated, which was located in the nucleus and highly expressed in fertility anthers. The silencing of TaGAMYB in wheat displayed fertility decline, defects in tapetum, pollen and exine formation, where the abortion characteristics were the same as YanZhan 4110S. In addition, either hot temperature or GA3 treatment in YanZhan 4110S caused the downregulation of TaGAMYB at binucleate stage and trinucleate stage, as well as fertility decrease. Further, the transcription factor TaWRKY2 significantly changed under GA3-treatment and directly interacted with the TaGAMYB promoter by W-box cis-element. Therefore, we suggested that TaGAMYB may be essential for anther development and male fertility, and GA3 activates TaGAMYB by TaWRKY2 to regulate fertility in wheat.

Imaging Flow Cytometry as a Quick and Effective Identification Technique of Pollen Grains from Betulaceae, Oleaceae, Urticaceae and Asteraceae

Despite the continuous and intensive development of laboratory techniques, a light microscope is still the most common tool used in pollen grains differentiation. However, microscopy is time-consuming and needs well-educated and experienced researchers. Other currently used techniques can be categorised as images and non-images analysis, but each has certain limitations. We propose a new approach to differentiate pollen grains using the Imaging Flow Cytometry (IFC) technique. It allows for high-throughput fluorescence data recording, which, in contrast to the standard FC, also enables real-time control of the results thanks to the possibility of digital image recording of cells flowing through the measuring capillary. The developed method allows us to determine the characteristics of the pollen grains population based on the obtained fluorescence data, using various combinations of parameters available in the IDEAS software, which can be analysed on different fluorescence channels. On this basis, we distinguished pollen grains both between and within different genera belonging to the Betulaceae, Oleaceae, Urticaceae and Asteraceae families. Thereby, we prove that the proposed methodology is sufficient for accurate, fast, and cost-effective identification and potentially can be used in the routine analysis of allergenic pollen grains.