Wheat male-sterile 2 reduces ROS levels to inhibit anther development by deactivating ROS modulator 1

Fertile grounds: exploring male sterility in cotton and its marker development

The high cost of producing conventional hybrid cotton seeds led to more research efforts on cotton male sterility systems. There is a lack of studies on cytology, histology, morphological variation, yield, and altered restorer backgrounds to identify and develop male sterility markers in cotton hybrids. Hybrid cotton can be efficiently produced by exploiting genetic male sterility. Among the 19 Genetic Male Sterility (GMS) genes discovered, the lines with ms5ms6 genes are mostly utilised to establish successful hybrid cotton in India. Molecular markers closely associated with the MS alleles are identified to facilitate the efficient and rapid backcrossing of male-sterility genes into elite lines or cultivars by marker-assisted backcrossing. The majority of the markers which are random DNA markers (RDMs), are probably lost, when recombination occurs. In contradiction, molecular markers (functional markers, or FMs) within the genic region can be identified and employed in crops for diverse traits, if prospective characteristic genes are known. In this review, the mechanism of male sterility, its gene expression level, and the need for functional markers for the male sterility trait in cotton have been put forward.

Wheat genomics: genomes, pangenomes, and beyond

There is an urgent need to improve wheat for upcoming challenges, including biotic and abiotic stresses. Sustainable wheat improvement requires the introduction of new genes and alleles in high-yielding wheat cultivars. Using new approaches, tools, and technologies to identify and introduce new genes in wheat cultivars is critical. High-quality genomes, transcriptomes, and pangenomes provide essential resources and tools to examine wheat closely to identify and manipulate new and targeted genes and alleles. Wheat genomics has improved excellently in the past 5 years, generating multiple genomes, pangenomes, and transcriptomes. Leveraging these resources allows us to accelerate our crop improvement pipelines. This review summarizes the progress made in wheat genomics and trait discovery in the past 5 years.

HSP70 and APX1 play important roles in cotton male fertility by mediating ROS homeostasis

Male sterility is used in the production of hybrid seeds and can improve the breeding efficiency of cotton hybrids. Reactive oxygen species is closely associated with the tapetum and pollen development, but their relationship in cotton male fertility remains unclear. In this study, we comprehensively compared the cytology and proteome of the anthers from an Upland cotton (Gossypium hirsutum) material, Shida 98 (WT), and its nearly-isogenic male sterile line Shida 98A (MS). Cytology indicated delayed PCD in the tapetum and defects in microspores in MS anthers. And further studies revealed disruption of ROS homeostasis. Proteomic analysis identified proteins with differential abundance mainly being related to redox homeostasis, protein folding, and apoptotic signaling pathways. GhAPX1 interacted with GhHSP70 and played a crucial role in the development of cotton anthers. Exogenous application of HSP70 inhibitor increased H2O2 content and decreased the activity of APX1 and pollen viability. The GhAPX1 mutants generated by CRISPR/Cas9-mediated gene editing exhibited premature degradation of the tapetum, significant decrease in pollen viability, and significant increase in H2O2 content. Altogether, our results imply HSP70 and APX1 being the key players jointly regulating male fertility by mediating ROS homeostasis. These results provide insights into the proteins associated with male fertility.

TaBZR1 enhances wheat salt tolerance via promoting ABA biosynthesis and ROS scavenging

Brassinosteroids (BRs) are vital plant steroid hormones involved in numerous aspects of plant life including growth, development, and responses to various stresses. However, the underlying mechanisms of how BR regulates abiotic stress responses in wheat (Triticum aestivum L.) remain to be elucidated. Here, we find that BR signal core transcription factor BRASSINAZOLE-RESISTANT1 (TaBZR1) is significantly up-regulated by salt treatment. Overexpression of Tabzr1-1D (a gain-of-function TaBZR1 mutant protein) improves wheat salt tolerance. Furthermore, we show that TaBZR1 binds directly to the G-box motif in the promoter of ABA biosynthesis gene TaNCED3 to activate its expression and promotes ABA accumulation. Moreover, TaBZR1 associates with the promoters of ROS-scavenging genes TaGPX2 and TaGPX3 to activate their expression. Taken together, our results elucidate that TaBZR1 improves salt-stress tolerance by activating some genes involved in the biosynthesis of ABA and ROS scavenging in wheat, which gives us a new strategy to improve the salt tolerance of wheat.

Spontaneous movement of a retrotransposon generated genic dominant male sterility providing a useful tool for rice breeding

Male sterility in plants provides valuable breeding tools in germplasm innovation and hybrid crop production. However, genetic resources for dominant genic male sterility, which hold great promise to facilitate breeding processes, are extremely rare in natural germplasm. Here we characterized the Sanming Dominant Genic Male Sterility in rice and identified the gene SDGMS using a map-based cloning approach. We found that spontaneous movement of a 1978-bp long terminal repeat (LTR) retrotransposon into the promoter region of the SDGMS gene activates its expression in anther tapetum, which causes abnormal programmed cell death of tapetal cells resulting in dominant male sterility. SDGMS encodes a ribosome inactivating protein showing N-glycosidase activity. The activation of SDGMS triggers transcription reprogramming of genes responsive to biotic stress leading to a hypersensitive response which causes sterility. The results demonstrate that an ectopic gene activation by transposon movement can give birth to a novel trait which enriches phenotypic diversity with practical utility.

Metal-organic framework-encapsulated dihydroartemisinin nanoparticles induces apoptotic cell death in ovarian cancer by blocking ROMO1-mediated ROS production

Dihydroartemisinin (DHA), a natural product derived from the herbal medicine Artemisia annua, is recently used as a novel anti-cancer agent. However, some intrinsic disadvantages limit its potential for clinical management of cancer patients, such as poor water solubility and low bioavailability. Nowadays, the nanoscale drug delivery system emerges as a hopeful platform for improve the anti-cancer treatment. Accordingly, a metal-organic framework (MOF) based on zeolitic imidazolate framework-8 was designed and synthesized to carry DHA in the core (ZIF-DHA). Contrast with free DHA, these prepared ZIF-DHA nanoparticles (NPs) displayed preferable anti-tumor therapeutic activity in several ovarian cancer cells accompanied with suppressed production of cellular reactive oxygen species (ROS) and induced apoptotic cell death. 4D-FastDIA-based mass spectrometry technology indicated that down-regulated reactive oxygen species modulator 1 (ROMO1) might be regarded as potential therapeutic targets for ZIF-DHA NPs. Overexpression of ROMO1 in ovarian cancer cells significantly reversed the cellular ROS-generation induced by ZIF-DHA, as well as the pro-apoptosis effects. Taken together, our study elucidated and highlighted the potential of zeolitic imidazolate framework-8-based MOF to improve the activity of DHA to treat ovarian cancer. Our findings suggested that these prepared ZIF-DHA NPs could be an attractive therapeutic strategy for ovarian cancer.

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.

A bifunctional selectable marker for wheat transformation contributes to the characterization of male-sterile phenotype induced by a synthetic Ms2 gene

KEY MESSAGE

An engineered selectable marker combining herbicide resistance and yellow fluorescence contributes to the characterization of male-sterile phenotype in wheat, the severity of which correlates with expression levels of a synthetic Ms2 gene. Genetic transformation of wheat is conducted using selectable markers, such as herbicide and antibiotic resistance genes. Despite their proven effectiveness, they do not provide visual control of the transformation process and transgene status in progeny, which creates uncertainty and prolongs screening procedures. To overcome this limitation, this study developed a fusion protein by combining gene sequences encoding phosphinothricin acetyltransferase and mCitrine fluorescent protein. The fusion gene, introduced into wheat cells by particle bombardment, enabled herbicide selection, and visual identification of primary transformants along with their progeny. This marker was then used to select transgenic plants containing a synthetic Ms2 gene. Ms2 is a dominant gene whose activation in wheat anthers leads to male sterility, but the relationship between the expression levels and the male-sterile phenotype is unknown. The Ms2 gene was driven either by a truncated Ms2 promoter containing a TRIM element or a rice promoter OsLTP6. The expression of these synthetic genes resulted in complete male sterility or partial fertility, respectively. The low-fertility phenotype was characterized by smaller anthers than the wild type, many defective pollen grains, and low seed sets. The reduction in the size of anthers was observed at earlier and later stages of their development. Consistently, Ms2 transcripts were detected in these organs, but their levels were significantly lower than those in completely sterile Ms2TRIM::Ms2 plants. These results suggested that the severity of the male-sterile phenotype was modulated by Ms2 expression levels and that higher levels may be key to activating total male sterility.