GhAIL6, a Member of the AP2 Family Gene, Promotes Somatic Embryogenesis in Cotton.

Background Somatic embryogenesis (SE) is the process by which plant somatic cells are cultured in vitro without fertilization to regenerate embryos and develop into intact plants, the difficulty of cotton regeneration has severely limited functional gene research and transgenic breeding. The AP2 family is a relatively large family of transcription factor genes that regulate the process of growth and development, but the role of Aintegumenta-Like6 ( AIL6) in cotton SE has not been reported. Methods The 35S::AIL6:GR vector was constructed and transformed into cotton JH713 by Agrobacterium-mediated method, after 3 years of self-breeding, stable genetic T3 generation positive plants were obtained, identified by Southern, and three lines were selected for the following regeneration experiments.Results The results showed that overexpression of GhAIL6 significantly inhibited the proliferation of callus during the first 30 days, and promoted the embryogenic callus production at about 45 days.Couclusion Our results indicated that GhAIL6 was a key regulator of cotton SE, overexpression of GhAIL6 helped to improve the regeneration efficiency of cotton SE

Agronomic and genetic approaches for enhancing tolerance to heat stress in rice: a review

Rice is an important cereal crop worldwide that serves as a dietary component for half of the world’s population. Climate change, especially global warming is a rising threat to crop production and food security. Therefore, enhancing rice growth and yield is a crucial challenge in stress-prone environments. Frequent episodes of heat stress threaten rice production all over the world. Breeders and agronomists undertake several techniques to ameliorate the adverse effects of heat stress to safeguard global rice production. The selection of suitable sowing time application of plant hormones, osmoprotectants and utilization of appropriate fertilizers and signaling molecules are essential agronomic practices to mitigate the adverse effects of heat stress on rice. Likewise, developing genotypes with improved morphological, biochemical, and genetic attributes is feasible and practical way to respond to this challenge. The creation of more genetic recombinants and the identification of traits responsible for heat tolerance could allow the selection of early-flowering cultivars with resistance to heat stress. This review details the integration of several agronomic, conventional breeding, and molecular approaches like hybridization, pure line selection, master-assisted-selection (MAS), transgenic breeding and CRRISPR/Cas9 that promise rapid and efficient development and selection of heat-tolerant rice genotypes. Such information’s could be used to determine the future research directions for rice breeders and other researchers working to improve the heat tolerance in rice.

Intact double stranded RNA is mobile and triggers RNAi against viral and fungal plant pathogens

Topical application of double-stranded RNA (dsRNA) as RNA interference(RNAi) based biopesticides represents a sustainable alternative to traditional transgenic, breeding-based or chemical crop protection strategies. A key feature of RNAi is its ability to act non-cell autonomously, a process that plays a critical role in plant protection. However, the uptake of dsRNA upon topical application, and its ability to move and act non-cell autonomously remains debated and largely unexplored. Here we show that when applied to a leaf, unprocessed full-length dsRNA enters the vasculature and rapidly moves to multiple distal below ground, vegetative and reproductive tissue types in several model plant and crop hosts. Intact unprocessed dsRNA was detected in the apoplast of leaves, roots and flowers after leaf application and maintained in subsequent new growth. Furthermore, we show mobile dsRNA is functional against root infecting fungal and foliar viral pathogens. Our demonstration of the uptake and maintained movement of intact and functional dsRNA stands to add significant benefit to the emerging field of RNAi-based plant protection.

Harnessing the Wild Relatives and Landraces for Fe and Zn Biofortification in Wheat through Genetic Interventions—A Review

Micronutrient deficiencies, particularly iron (Fe) and zinc (Zn), in human diets are affecting over three billion people globally, especially in developing nations where diet is cereal-based. Wheat is one of several important cereal crops that provide food calories to nearly one-third of the population of the world. However, the bioavailability of Zn and Fe in wheat is inherently low, especially under Zn deficient soils. Although various fortification approaches are available, biofortification, i.e., development of mineral-enriched cultivars, is an efficient and sustainable approach to alleviate malnutrition. There is enormous variability in Fe and Zn in wheat germplasm, especially in wild relatives, but this is not utilized to the full extent. Grain Fe and Zn are quantitatively inherited, but high-heritability and genetic correlation at multiple locations indicate the high stability of Fe and Zn in wheat. In the last decade, pre-breeding activities have explored the potential of wild relatives to develop Fe and Zn rich wheat varieties. Furthermore, recent advances in molecular biology have improved the understanding of the uptake, storage, and bioavailability of Fe and Zn. Various transportation proteins encoding genes like YSL 2, IRT 1, OsNAS 3, VIT 1, and VIT 2 have been identified for Fe and Zn uptake, transfer, and accumulation at different developing stages. Hence, the availability of major genomic regions for Fe and Zn content and genome editing technologies are likely to result in high-yielding Fe and Zn biofortified wheat varieties. This review covers the importance of wheat wild relatives for Fe and Zn biofortification, progress in genomics-assisted breeding, and transgenic breeding for improving Fe and Zn content in wheat.

AaWRKY17, a positive regulator of artemisinin biosynthesis, is involved in resistance to Pseudomonas syringae in Artemisia annua

Artemisia annua, a traditional Chinese medicinal plant, remains the only plant source for artemisinin production, yet few genes have been identified to be involved in both the response to biotic stresses, such as pathogens, and artemisinin biosynthesis. Here, we isolated and identified the WRKY transcription factor (TF) AaWRKY17, which could significantly increase the artemisinin content and resistance to Pseudomonas syringae in A. annua. Yeast one-hybrid (Y1H), dual-luciferase (dual-LUC), and electrophoretic mobility shift assay (EMSA) results showed that AaWRKY17 directly bound to the W-box motifs in the promoter region of the artemisinin biosynthetic pathway gene amorpha-4,11-diene synthase (ADS) and promoted its expression. Real-time quantitative PCR (RT-qPCR) analysis revealed that the transcript levels of two defense marker genes, Pathogenesis-Related 5 (PR5) and NDR1/HIN1-LIKE 10 (NHL10), were greatly increased in AaWRKY17-overexpressing transgenic A. annua plants. Additionally, overexpression of AaWRKY17 in A. annua resulted in decreased susceptibility to P. syringae. These results indicated that AaWRKY17 acted as a positive regulator in response to P. syringae infection. Together, our findings demonstrated that the novel WRKY transcription factor AaWRKY17 could potentially be used in transgenic breeding to improve the content of artemisinin and pathogen tolerance in A. annua.

The Development of Herbicide Resistance Crop Plants Using CRISPR/Cas9-Mediated Gene Editing

The rapid increase in herbicide-resistant weeds creates a huge challenge to global food security because it can reduce crop production, causing considerable losses. Combined with a lack of novel herbicides, cultivating herbicide-resistant crops becomes an effective strategy to control weeds because of reduced crop phytotoxicity, and it expands the herbicidal spectrum. Recently developed clustered regularly interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas)-mediated genome editing techniques enable efficiently targeted modification and hold great potential in creating desired plants with herbicide resistance. In the present review, we briefly summarize the mechanism responsible for herbicide resistance in plants and then discuss the applications of traditional mutagenesis and transgenic breeding in cultivating herbicide-resistant crops. We mainly emphasize the development and use of CRISPR/Cas technology in herbicide-resistant crop improvement. Finally, we discuss the future applications of the CRISPR/Cas system for developing herbicide-resistant crops.

Generation of Marker-Free Transgenic Rice Resistant to Rice Blast Disease Using Ac/Ds Transposon-Mediated Transgene Reintegration System

Rice blast is one of the most serious diseases of rice and a major threat to rice production. Breeding disease-resistant rice is one of the most economical, safe, and effective measures for the control of rice blast. As a complement to traditional crop breeding, the transgenic method can avoid the time-consuming process of crosses and multi-generation selection. In this study, maize (Zea mays) Activator (Ac)/Dissociation (Ds) transposon vectors carrying green fluorescent protein (GFP) and red fluorescent protein (mCherry) genetic markers were used for generating marker-free transgenic rice. Double fluorescent protein-aided counterselection against the presence of T-DNA was performed together with polymerase chain reaction (PCR)-based positive selection for the gene of interest (GOI) to screen marker-free progeny. We cloned an RNAi expression cassette of the rice Pi21 gene that negatively regulates resistance to rice blast as a GOI into the Ds element in the Ac/Ds vector and obtained marker-free T1 rice plants from 13 independent transgenic lines. Marker-free and Ds/GOI-homozygous rice lines were verified by PCR and Southern hybridization analysis to be completely free of transgenic markers and T-DNA sequences. qRT-PCR analysis and rice blast disease inoculation confirmed that the marker-free transgenic rice lines exhibited decreased Pi21 expression levels and increased resistance to rice blast. TAIL-PCR results showed that the Ds (Pi21-RNAi) transgenes in two rice lines were reintegrated in intergenic regions in the rice genome. The Ac/Ds vector with dual fluorescent protein markers offers more reliable screening of marker-free transgenic progeny and can be utilized in the transgenic breeding of rice disease resistance and other agronomic traits.

BREVIPEDICELLUS and ERECTA mediate expression ofAtPRX17in preventing Arabidopsis callus retardation and browning

ABSTRACTEfficient in vitro callus generation is fundamental to tissue culture propagation, a process required for plant regeneration and transgenic breeding for desired phenotypes. Identifying genes and regulatory elements that prevent callus retardation and browning is essential to facilitate the development of vitro callus systems. Here we show thatBREVIPEDICELLUS(BP) andERECTA(ER) pathways inArabidopsiscallus are converged to prevent callus browning and positively regulate an isoperoxidase gene AtPRX17expression in the rapid growth callus. Loss of functions in bothBPandERresulted in markedly increasing callus browning. Transgenic lines withpro35S::AtPRX17in thebp-5 er105double mutant background fully rescued this phenotypic abnormality. Using plantin vitroDNA-binding assays, we observed that BP protein bound directly to the upstream sequence ofAtPRX17to promote its transcription during callus growth. ER is a universally presenting factor required for cell proliferation and growth, we show thatERpositively regulates expression of a transcription factorWRKY6, which also directly binds to an additional site of the AtPRX17promoter for its high expression. Our data reveals an important molecular mechanism in regulating expression of peroxidase isozyme to reduce Arabidopsis callus browning.HighlightBREVIPEDICELLUSandERECTAare involved in regulating Arabidopsis callus browning by controlling expression ofAtPRX17.

Recent Advances in Understanding Mechanisms of Plant Tolerance and Response to Aluminum Toxicity

Aluminum (Al) toxicity is a major environmental stress that inhibits plant growth and development. There has been impressive progress in recent years that has greatly increased our understanding of the nature of Al toxicity and its mechanisms of tolerance. This review describes the transcription factors (TFs) and plant hormones involved in the adaptation to Al stress. In particular, it discusses strategies to confer plant resistance to Al stress, such as transgenic breeding, as well as small molecules and plant growth-promoting rhizobacteria (PGPRs) to alleviate Al toxicity. This paper provides a theoretical basis for the enhancement of plant production in acidic soils.

Foxtail Millet Stress Associated Protein Gene SiSAP4 Enhances Drought Stress Tolerance in Transgenic Arabidopsis

Abiotic stresses like drought affect plant growth and crop yield with climate change worsening. Stress associated proteins (SAPs), as the zinc finger proteins with A20/AN1 domain, play an important role in regulating abiotic stress response. As a typical summer dryland grain crop in the north of China, foxtail millet has the characteristics of drought resistance, making it a valuable resource for anti-stress gene exploitation and utilization. In this study, SiSAP4 gene was cloned from foxtail millet variety Yugu 1. Analysis showed that SiSAP4 gene was expressed in roots, stems and leaves at seedling stage, and the highest expression level was detected in leaves. Expression patterns under different stress conditions showed that expression level of SiSAP4 gene was significantly up-regulated under drought stress, suggesting it may be involved in drought stress response. Subcellular localization indicated that SiSAP4 was present in the nucleus and cytoplasm. It was revealed that SiSAP4 had no function in transcriptional activation in the yeast system. Overexpression of SiSAP4 in transgenic Arabidopsis resulted in enhanced tolerance to drought stress, which was simultaneously demonstrated by increased expression of a broad range of stress response genes. Based on those results, SiSAP4 has the potential to be used in transgenic breeding to improve drought stress tolerance in other crops. © 2021 Friends Science Publishers