Electrophysiological, Morphologic, and Transcriptomic Profiling of the Ogura-CMS, DGMS and Maintainer Broccoli Lines

Advances in and Perspectives on Transgenic Technology and CRISPR-Cas9 Gene Editing in Broccoli

Broccoli, a popular international Brassica oleracea crop, is an important export vegetable in China. Broccoli is not only rich in protein, vitamins, and minerals but also has anticancer and antiviral activities. Recently, an Agrobacterium-mediated transformation system has been established and optimized in broccoli, and transgenic transformation and CRISPR-Cas9 gene editing techniques have been applied to improve broccoli quality, postharvest shelf life, glucoraphanin accumulation, and disease and stress resistance, among other factors. The construction and application of genetic transformation technology systems have led to rapid development in broccoli worldwide, which is also good for functional gene identification of some potential traits in broccoli. This review comprehensively summarizes the progress in transgenic technology and CRISPR-Cas9 gene editing for broccoli over the past four decades. Moreover, it explores the potential for future integration of digital and smart technologies into genetic transformation processes, thus demonstrating the promise of even more sophisticated and targeted crop improvements. As the field continues to evolve, these innovations are expected to play a pivotal role in the sustainable production of broccoli and the enhancement of its nutritional and health benefits.

Exogenous application of glutathione enhanced growth, nutritional orchestration and physiochemical characteristics of Brassica oleracea L. under lead stress

A major obstacle to agricultural production and yield quality is heavy metal contamination of the soil and water, which leads to lower productivity and quality of crops. The situation has significantly worsened as a result of the growing population and subsequent rise in food consumption. The growth of nutrient-rich plants is hampered by lead (Pb) toxicity in the soil. Brassica oleracea L. (broccoli) is a prominent vegetable crop in the Brassicaceae family subjected to a number of biotic and abiotic stresses that dramatically lower crop yields. Seed priming is a novel, practicable, and cost-effective method that can improve various abiotic stress tolerances. Many plant metabolic activities depend on the antioxidant enzyme glutathione (GSH), which also chelates heavy metals. Keeping in view the stress mitigation potential of GSH, current research work was designed to inspect the beneficial role of seed priming with GSH on the growth, morphological and gas exchange attributes of broccoli seedlings under Pb stress. For this purpose, broccoli seeds were primed with 25, 50, and 75 µM L-1 GSH. Plant growth and photosynthetic activity were adversely affected by Pb stress. Furthermore, Pb stress enhanced proline levels along with reduced protein and phenol content. The application of GSH improved growth traits, total soluble proteins, chlorophyll content, mineral content, and gas exchange parameters. The involvement of GSH in reducing Pb concentrations was demonstrated by an improved metal tolerance index and lower Pb levels in broccoli plants. The results of the current study suggest that GSH can be used as a strategy to increase broccoli tolerance to Pb by enhancing nutrient uptake, growth and proline.

A high-efficiency PEG-Ca2+-mediated transient transformation system for broccoli protoplasts

Transient transformation of plant protoplasts is an important method for studying gene function, subcellular localization and plant morphological development. In this study, an efficient transient transformation system was established by optimizing the plasmid concentration, PEG4000 mass concentration and genotype selection, key factors that affect transformation efficiency. Meanwhile, an efficient and universal broccoli protoplast isolation system was established. Using 0.5% (w/v) cellulase R-10 and 0.1% (w/v) pectolyase Y-23 to hydrolyze broccoli cotyledons of three different genotypes for 3 h, the yield was more than 5×10⁶/mL/g, and the viability was more than 95%, sufficient to meet the high standards for protoplasts to be used in various experiments. The average transformation efficiency of the two plasmid vectors PHG-eGFP and CP507-YFP in broccoli B1 protoplasts were 61.4% and 41.7%, respectively. Using this system, we successfully performed subcellular localization of the products of three target genes (the clubroot resistance gene CRa and two key genes regulated by glucosinolates, Bol029100 and Bol031350).The results showed that the products of all three genes were localized in the nucleus. The high-efficiency transient transformation system for broccoli protoplasts constructed in this study makes it possible to reliably acquire high-viability protoplasts in high yield. This research provides important technical support for international frontier research fields such as single-cell sequencing, spatial transcriptomics, plant somatic hybridization, gene function analysis and subcellular localization.

Transcriptomic and iTRAQ-Based Quantitative Proteomic Analyses of inap CMS in Brassica napus L

Brassica napus inap cytoplasmic male sterility (CMS) is a novel sterile line with potential application in rapeseed hybrid breeding. Sterile cytoplasm was obtained from Isatis indigotica through somatic fusion and then recurrent backcrossing with B. napus. Previous studies have shown that inap CMS abortion occurred before the stamen primordia (stage 4–5), but the genetic mechanism of sterility needs to be studied. RNA-seq analyses were performed on the floral buds at two stages (0–5 and 6–8), before and after the formation of stamen primordium. As a result, a total of 1769 and 594 differentially expressed genes (DEGs) were detected in the CMS line compared to its maintainer line at the two stages, respectively. In accordance with the CMS phenotype, the up- and downstream regulators of the stamen identity genes AP3 and PI were up- and downregulated in the CMS line, respectively. Furthermore, isobaric tags for relative and absolute quantitation (iTRAQ) analysis showed that a total of 760 differentially abundant proteins (DAPs) were identified in flower buds at stages 0–8, and most of the proteins related to the anther development, oxidative phosphorylation, and programmed cell death (PCD) were downregulated in inap CMS. In combined transcriptomic and proteomic analysis, a total of 32 DEGs/DAPs were identified, of which 7 common DEGs/DAPs had the same expression trend at stage 0–8 of flower development. The downregulation of genes related to the energy deficiency, hormone signal transduction, and the maintenance of mitochondrial metabolic homeostasis at stage 0–5 might disturb the normal differentiation of stamen primordium, resulting in carpelloid stamen of inap CMS. The study will help provide insights into the molecular mechanism of this new male sterility.

Genetic Diversity and DNA Fingerprinting in Broccoli Carrying Multiple Clubroot Resistance Genes Based on SSR Markers

To identify cultivars quickly and accurately, DNA fingerprinting of 10 broccoli varieties was performed by using simple sequence repeat (SSR) marker technology. Highly informative and polymorphic SSR markers were screened using broccoli and rapeseed. Out of the 93 SSR marker pairs, 21 pairs were selected and found to have good polymorphism. Each marker pair generated 1 to 10 polymorphic bands with an average of 4.29. The average polymorphism information content (PIC) was 0.41 with a range from 0.16 to 0.95. Six selected marker pairs established the fingerprinting of the 10 accessions and their unique fingerprints. Cluster analysis of 10 accessions showed that the genetic similarity coefficient was between 0.57 and 0.91. They can be divided into 3 groups at the genetic similarity coefficient (GSC) of 0.73. The above results indicated that DNA fingerprinting could provide a scientific basis for the identification of broccoli polymerized multiple clubroot resistance genes. Research shows that SSR marker-based DNA fingerprinting further ensures plant seed purity.