Phenylpropanoid pathway in plants and its role in response to heavy metal stress: a review / 生物工程学报

Phenylpropanoid metabolic pathway is one of the most important secondary metabolic pathways in plants. It directly or indirectly plays an antioxidant role in plant resistance to heavy metal stress, and can improve the absorption and stress tolerance of plants to heavy metal ions. In this paper, the core reactions and key enzymes of the phenylpropanoid metabolic pathway were summarized, and the biosynthetic processes of key metabolites such as lignin, flavonoids and proanthocyanidins and relevant mechanisms were analyzed. Based on this, the mechanisms of key products of phenylpropanoid metabolic pathway in response to heavy metal stress were discussed. The perspectives on the involvement of phenylpropanoid metabolism in plant defense against heavy metal stress provides a theoretical basis for improving the phytoremediation efficiency of heavy metal polluted environment.

Influence of Chromium Stress on Chlorophyll Content, Polyphenol Oxidase and Peroxidase Activity in Horse Gram (Dolichos biflorus L)

The presence of heavy metals in solid and liquid wastes is a significant issue in terms of the environment degradation. These are one of the most serious environmental pollutants, and reaching dangerous levels will need more investigation. Chromium, in particular, has become a global environmental problem among heavy metals. This research looked at the effects of Cr207 stress on Dolichos biflorus L., a kind of horse grain that plays an essential role in Indian agriculture. D. biflorus seeds were cultivated in the dark under laboratory conditions with a Sodium chromate concentration of (0-3.0mg/L). The control treatment was distilled water. Seven-day-old seedlings were utilized to study the effects of chromate stress on peroxidase activity and chlorophyll content. The findings showed that when the quantity of Sodium chromate increased, the chlorophyll content of D. biflorus seedlings increased considerably (p 0.9). Increased polyphenyloxiase and peroxidase activity indicated the appearance of a scavenging mechanism in plants under heavy metal stress, whereas increased peroxidase quantity indicated the generation of free radicals. The drop in chlorophyll concentration indicates that the plants' development has slowed, resulting in a fall in production.

Genome-wide analysis of metallothionein gene family in maize to reveal its role in development and stress resistance to heavy metal

BACKGROUND: Maize (Zea mays L.) is a widely cultivated cereal and has been used as an optimum heavy metal phytoremediation crop. Metallothionein (MT) proteins are small, cysteine-rich, proteins that play important roles in plant growth and development, and the regulation of stress response to heavy metals. However, the MT genes for maize have not been fully analyzed so far. METHODS: The putative ZmMT genes were identified by HMMER. The heat map of ZmMT genes spatial expression analysis was generated by using R with the log2 (FPKM + 1). The expression profiles of ZmMT genes under three kinds of heavy metal stresses were quantified by using qRT-PCR. The metallothionein proteins was aligned using MAFFT and phylogenetic analysis were constructed by ClustalX 2.1. The protein theoretical molecular weight and pI, subcellular localization, TFs binding sites, were predicted using ProtParam, PSORT, PlantTFDB, respectively. RESULTS: A total of 9 ZmMT genes were identified in the whole genome of maize. The results showed that eight of the nine ZmMT proteins contained one highly conserved metallothio_2 domain, while ZmMT4 contained a Metallothio_PEC domain. All the ZmMT proteins could be classified into three major groups and located on five chromosomes. The ZmMT promoters contain a large number of hormone regulatory elements and hormone-related transcription factor binding sites. The ZmMT genes exhibited spatiotemporal specific expression patterns in 23 tissues of maize development stages and showed the different expression patterns in response to Cu, Cd, and Pb heavy metal stresses. CONCLUSIONS: We identified the 9 ZmMT genes, and explored their conserved motif, tissue expression patterns, evolutionary relationship. The expression profiles of ZmMT genes under three kinds of heavy metal stresses (Cu, Cd, Pb) were analyzed. In summary, the expression of ZmMTs have poteintial to be regulated by hormones. The specific expression of ZmMTs in different tissues of maize and the response to different heavy metal stresses are revealed that the role of MT in plant growth and development, and stress resistance to heavy metals.

Cadmium toxicity affects chlorophyll a and b content, antioxidant enzyme activities and mineral nutrient accumulation in strawberry

BACKGROUND: Cadmium (Cd) is well known as one of the most toxic metals affecting the environment and can severely restrict plant growth and development. In this study, Cd toxicities were studied in strawberry cv. Camarosa using pot experiment. Chlorophyll and malondialdehyde (MDA) contents, catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) activities and mineral nutrient concentrations were investigated in both roots and leaves of strawberry plant after exposure Cd. RESULTS: Cd content in both roots and leaves was increased with the application of increasing concentrations of Cd. We found higher Cd concentration in roots rather than in leaves. Chlorophyll a and b was decreased in leaves but MDA significantly increased under increased Cd concentration treatments in both roots and leaves. SOD and CAT activities was also increased with the increase Cd concentrations. K, Mn and Mg concentrations were found higher in leaves than roots under Cd stress. In general, increased Cd treatments increased K, Mg, Fe, Ca, Cu and Zn concentration in both roots and leaves. Excessive Cd treatments reduced chlorophyll contents, increased antioxidant enzyme activities and changes in plant nutrition concentrations in both roots and leaves. CONCLUSION: The results presented in this work suggested that Cd treatments have negative effect on chlorophyll content and nearly decreased 30% of plant growth in strawberry. Strawberry roots accumulated higher Cd than leaves. We found that MDA and antioxidant enzyme (CAT, SOD and APX) contents may have considered a good indicator in determining Cd tolerance in strawberry plant.

Chromium accumulation potential of Zea mays grown under four different fertilizers.

Chromium (Cr) contamination in soil is a growing concern in sustainable agriculture production and food safety. We performed pot experiment with chromium (30 mg/ soil) to assess the accumulation potential of Zea mays and study the influence of four fertilizers, viz. Farm Yard Manure (FYM), NPK, Panchakavya (PK) and Vermicompost (VC) with respect to Cr accumulation. The oxidative stress and pigment (chlorophyll) levels were also examined. The results showed increased accumulation of chromium in both shoots and roots of Zea mays under FYM and NPK supply, and reduced with PK and VC. While the protein and pigment contents decreased in Cr treated plants, the fertilizers substantiated the loss to overcome the stress. Similarly, accumulation of Cr increased the levels of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) indicating the enhanced damage control activity. However, these levels were relatively low in plants supplemented with fertilizers. Our results confirm that the maize can play an effective role in bioremediation of soils polluted with chromium, particularly in supplementation with fertilizers such as farm yard manure and NPK.

Zinc and copper induced changes in physiological characteristics of Vigna mungo (L.).

The effect of deleterious concentration of zinc and copper provided either individually or in combination in the nutrient media was investigated in order to assess the effect of metal interaction in Vigna mungo (L.). Both metals showed negative effect and led to a marked decrease in seed germination (20%), seedling growth (91.7%) and nitrate reductase activity (85.7%) with the increase in metal concentrations. The present study also emphasizes on the response of catalase and peroxidase enzyme under zinc and copper stress. Both antioxidant enzymes exhibited an increasing trend under different treatment conditions but it was reverse at highly toxic metal concentration. The results showed active involvement of peroxidase enzyme in regulating oxidative stress rather than catalase enzyme, as the specific activity of peroxidase enzyme got increased by 8.94% under the combined metals stress whereas catalase activity got declined by 60.97% in comparison to control due to excessive stress. The combined effect of copper and zinc metal was more pronounced in comparison to their individual effects.

Ascorbic acid: an enigmatic molecule to developmental and environmental stress in plant.

Ascorbic acid (AA) is present in all eukaryotes including animals and plants and lack completely in prokaryotes with exception of cyanobactaria. Today, AA has gained significant place in plant science, mainly due to its properties (antioxidant and cellular reductant etc.), and multifunctional roles in plant growth, development, and regulation of large spectrum of plant defense mechanisms against environmental stresses. Some studies suggests that the endogenous AA has been implicated in the promotion of plant growth and development by involving in a complex array of phytohormonemediated signaling networks that ties together various developmental and environmental stresses. In the last few years, the role of AA in tolerance of plants to environmental stress has established much consideration. As it is evident from the present review, recent progress on AA potentiality in tolerance of plants to environmental stresses has been impressive. Indeed, AA also plays an important role in resistance to developmental programmes (stresses, e.g., bud induction, flowering and senescence) and environmental stresses (e.g., osmotic, temperature, pathogenesis and weedicides and herbicides).