Selection for low-cadmium cultivars and cadmium subcellular distribution comparison between two selected cultivars of eggplant (Solanum melongena L.)

Bulk Segregant Analysis Sequencing and RNA-Seq Analyses Reveal Candidate Genes Associated with Sepal Color Phenotype of Eggplant (Solanum melongena L.)

Eggplant is a highly significant vegetable crop and extensively cultivated worldwide. Sepal color is considered one of the major commercial traits of eggplant. Eggplant sepals develop from petals, and sepals have the ability to change color by accumulating anthocyanins, but whether the eggplants in sepal and their biosynthetic pathways are the same as those in petals is not known. To date, little is known about the underlying mechanisms of sepal color formation. In this study, we performed bulked segregant analysis and transcriptome sequencing using eggplant sepals and obtained 1,452,898 SNPs and 182,543 InDel markers, respectively, as well as 123.65 Gb of clean data using transcriptome sequencing. Through marker screening, the genes regulating eggplant sepals were localized to an interval of 2.6 cM on chromosome 10 by bulked segregant analysis sequencing and transcriptome sequencing and co-analysis, combined with screening of molecular markers by capillary electrophoresis. Eight possible candidate genes were then screened to further interpret the regulatory incentives for the eggplant sepal color.

Physiological and biochemical characteristics of high and low Cd accumulating Brassica napus genotypes

Phytoremediation is a widely used and cost-effective technique for in situ remediation of heavy metals. Brassica napus L. genotype with high Cd accumulation and strong Cd tolerance is an ideal candidate for phytoremediation. In this study, a hydroponic experiment was conducted to select a Brassica napus genotype with either high or low Cd accumulation from a panel of 55 genotypes. The physiological mechanisms governing Cd accumulation and Cd tolerance were then explored. BN400 and BN147 were identified as the high and low Cd accumulating genotypes, respectively. Additionally, BN400 exhibited greater tolerance to Cd stress compared to BN147. Root morphology analysis revealed that BN400 exhibited longer root length, smaller root surface area and root volume, and less root tips but bigger root diameter than BN147. Subcellular Cd distribution showed that the Cd concentrations in the cell wall and vacuole in shoot were significantly higher in BN400 than in BN147, whereas the opposite trend was observed in the roots.. Pectate/protein-integrated Cd was found to be the predominant form of Cd in both shoots and roots, with significantly higher levels in BN400 compared to BN147 in the shoot, but the opposite trend was observed in the roots. These results suggest that the long fine roots play a role in Cd accumulation. The high Cd accumulating genotype was able to retain Cd in leaf cell walls and vacuoles, and Cd was mainly present in the form of pectate/protein-integrated Cd, which contributes to its strong Cd tolerance. These findings have important implications for the screening and breeding of Brassica napus genotypes with high Cd accumulation for phytoremediation purposes.

Effects of different water conditions on the cadmium hyperaccumulation efficiency of Rorippa sylvestris (L.) Besser and Rorippa amphibia Besser

Increasing the translocation and accumulation of cadmium (Cd) in Cd hyperaccumulator is an important technology to improve the phytoremediation efficiency of Cd-contaminated soil. In order to investigate the effects of different water conditions on the growth and Cd accumulation ability of Cd hyperaccumulators Rorippa sylvestris (L.) Besser and Rorippa amphibia Besser in Cd-polluted soil, clone seedlings of them were transplanted into pots filled with 50 mg kg^-1 Cd-contaminated soil and cultured with water conditions of soil relative water content (RWC) 35%, 55%, 75%, 95%, and flooding respectively. The results showed the following: with the increase of RWC, the height of R. sylvestris and R. amphibia increased gradually, the dry biomass of shoot and whole plant increased and reached the maximum in 95% and then decreased in flooding; the Cd concentrations in shoots of R. sylvestris and R. amphibia were more than 100 mg kg^-1 except for 35% and flooding; Cd bioconcentration factors (BCFs) of R. amphibia reached the maximum of 3.8870 in 75% and R. sylvestris reached the maximum of 3.2330 in 95%; sufficient water resulted in the decrease of photosynthetic rate due to more Cd accumulation. However, under flooding condition, because of the decrease of Cd bioavailability in soil, the accumulation of Cd in shoots declined and the net photosynthetic rate (P_n) enhanced slightly.

Characterization of cadmium accumulation mechanism between eggplant (Solanum melongena L.) cultivars

Excessive cadmium (Cd) accumulation in vegetables due to farmland pollution constitutes a serious threat to human health. Eggplant has a tendency to accumulate Cd. To investigate the mechanism of the differences in Cd accumulation levels between high-Cd (BXGZ) and low-Cd (MYQZ) eggplant cultivar, physiological and biochemical indicators and mRNA expression of eggplant were examined using photosynthetic apparatus, biochemical test kits, Fourier transform infrared (FTIR) spectroscopy and transcriptome sequencing, etc. The results of biochemical test kits and FTIR revealed that MYQZ enhanced pectin methylesterase (PME) activity, and lignin and pectin content in the root cell wall, which was associated with the upregulation of PME, cinnamyl-alcohol dehydrogenase and peroxidase (PODs). Higher levels of cysteine and glutathione (GSH) contents and upregulation of genes associated with sulfur metabolism, as well as higher expression of ATP-binding cassette transporters (ABCs), cation exchangers (CAX) and metal tolerance proteins (MTPs) were observed in MYQZ. In BXGZ, the higher stomatal density and stomatal aperture as well as higher levels of Ca²⁺ binding protein-1 (PCaP1) and aquaporins and lower levels of A2-type cyclins (CYCA2-1) are consistent with an enhanced transpiration rate in BXGZ. Furthermore, a more developed root system was shown to be associated with higher levels of auxin response factor (ARF19), GATA transcription factors (GATA4, 5 and 11) and auxin efflux carrier component (PIN5) in BXGZ. In conclusion, highly active PME, and higher levels of lignin and pectin in MYQZ are expected to reduce Cd toxicity, while Cd translocation can be inhibited with the help of ABC and other Cd transporters. As for BXGZ, the uptake and translocation of Cd were enhanced by the developed root system and stronger transpiration.