Study on phytotoxicity evaluation and physiological properties of nicosulfuron on sugar beet (Beta vulgaris L.)

Genome-wide analysis of the common bean (Phaseolus vulgaris) laccase gene family and its functions in response to abiotic stress

BACKGROUND

Laccase (LAC) gene family plays a pivotal role in plant lignin biosynthesis and adaptation to various stresses. Limited research has been conducted on laccase genes in common beans.

RESULTS

29 LAC gene family members were identified within the common bean genome, distributed unevenly in 9 chromosomes. These members were divided into 6 distinct subclades by phylogenetic analysis. Further phylogenetic analyses and synteny analyses indicated that considerable gene duplication and loss presented throughout the evolution of the laccase gene family. Purified selection was shown to be the major evolutionary force through Ka / Ks. Transcriptional changes of PvLAC genes under low temperature and salt stress were observed, emphasizing the regulatory function of these genes in such conditions. Regulation by abscisic acid and gibberellins appears to be the case for PvLAC3, PvLAC4, PvLAC7, PvLAC13, PvLAC14, PvLAC18, PvLAC23, and PvLAC26, as indicated by hormone induction experiments. Additionally, the regulation of PvLAC3, PvLAC4, PvLAC7, and PvLAC14 in response to nicosulfuron and low-temperature stress were identified by virus-induced gene silence, which demonstrated inhibition on growth and development in common beans.

CONCLUSIONS

The research provides valuable genetic resources for improving the resistance of common beans to abiotic stresses and enhance the understanding of the functional roles of the LAC gene family.

Distinctive physiological and molecular responses of foxtail millet and maize to nicosulfuron

Introduction

Nicosulfuron is the leading acetolactate synthase inhibitor herbicide product, and widely used to control gramineous weeds. Here, we investigated the metabolic process of nicosulfuron into foxtail millet and maize, in order to clarify the mechanism of the difference in sensitivity of foxtail millet and maize to nicosulfuron from the perspective of physiological metabolism and provide a theoretical basis for the breeding of nicosulfuron-resistant foxtail millet varieties.

Methods

We treated foxtail millet (Zhangzagu 10, Jingu 21) and maize (Nongda 108, Ditian 8) with various doses of nicosulfuron in both pot and field experiments. The malonaldehyde (MDA) content, target enzymes, detoxification enzymes, and antioxidant enzymes, as well as related gene expression levels in the leaf tissues of foxtail millet and maize were measured, and the yield was determined after maturity.

Results

The results showed that the recommended dose of nicosulfuron caused Zhangzagu 10 and Jingu 21 to fail to harvest; the yield of the sensitive maize variety (Ditian 8) decreased by 37.09%, whereas that of the resistant maize variety (Nongda 108) did not decrease. Nicosulfuron stress increased the CYP450 enzyme activity, MDA content, and antioxidant enzyme activity of foxtail millet and maize, reduced the acetolactate synthase (ALS) activity and ALS gene expression of foxtail millet and Ditian 8, and reduced the glutathione S-transferase (GST) activity and GST gene expression of foxtail millet. In conclusion, target enzymes, detoxification enzymes, and antioxidant enzymes were involved in the detoxification metabolism of nicosulfuron in plants. ALS and GST are the main factors responsible for the metabolic differences among foxtail millet, sensitive maize varieties, and resistant maize varieties.

Discussion

These findings offer valuable insights for exploring the target resistance (TSR) and non-target resistance (NTSR) mechanisms in foxtail millet under herbicide stress and provides theoretical basis for future research of develop foxtail millet germplasm with diverse herbicide resistance traits.

Review on the Discovery of Novel Natural Herbicide Safeners

The phytotoxicity of herbicides on crops is a major dilemma in agricultural production. Fortunately, the emergence of herbicide safeners is an excellent solution to this challenge, selectively enhancing the performance of herbicides in controlling weeds while reducing the phytotoxicity to crops. But owing to their potential toxicity, only a tiny proportion of safeners are commercially available. Natural products as safeners have been extensively explored, which are generally safe to mammals and cause little pollution to the environment. They are typically endogenous signal molecules or phytohormones, which are generally difficult to extract and synthesize, and exhibit relatively lower activity than commercial products. Therefore, it is necessary to adopt rational design approaches to modify the structure of natural safeners. This paper reviews the application, safener effects, structural characteristics, and modifications of natural safeners and provides insights on the discovery of natural products as potential safeners in the future.

Effect of nicosulfuron on dynamic changes in the starch-sugar interconversion in sweet maize (Zea mays L.)

Starch is an important reserve of sugar, and starch-sugar conversion in plants plays an important role in the response of plants to various abiotic stresses. Nicosulfuron is a post-emergence herbicide commonly applied to maize fields. However, it is unclear how sucrose and starch in sweet corn are converted to accommodate nicosulfuron stress. Field and pot experiments were conducted to study the effects of nicosulfuron on the sugar metabolism enzymes, starch metabolism enzymes, non-enzyme substances, and expression of key enzyme genes in leaves and roots of sweet maize seedlings. Accordingly, this research compared the responses of the sister lines HK301 and HK320, which are nicosulfuron tolerant and sensitive, respectively. Under nicosulfuron stress, compared with HK301 seedlings, the accumulation of stem and root dry matter of HK320 seedlings was significantly reduced, resulting in a lower root-to-shoot ratio. Compared with HK320 seedlings, nicosulfuron stress significantly increased the sucrose, soluble sugar, and starch contents in HK301 leaves and roots. This may be related to the enhanced carbohydrate metabolism under nicosulfuron stress, including significant changes in sugar metabolism enzyme activity and the levels of SPS and SuSys expression. Further, under nicosulfuron stress, sucrose transporter genes (SUC 1, SUC 2, SWEET 13a, and SWEET 13b) in the leaves and roots of HK301 seedlings were significantly upregulated. Our results emphasize that changes in sugar distribution, metabolism, and transport can improve the adaptability of sweet maize to nicosulfuron stress.

Effect of boron deficiency on the photosynthetic performance of sugar beet cultivars with contrasting boron efficiencies

Boron (B) deficiency severely affects the quality of sugar beet production, and the employment of nutrient-efficient varieties for cultivation is a crucial way to solve environmental and resource-based problems. However, the aspect of leaf photosynthetic performance among B-efficient sugar beet cultivars remains uncertain. The B deficient and B-sufficient treatments were conducted in the experiment using KWS1197 (B-efficient) and KWS0143 (B-inefficient) sugar beet cultivars as study materials. The objective of the present study was to determine the impacts of B deficiency on leaf phenotype, photosynthetic capacity, chloroplast structure, and photochemical efficiency of the contrasting B-efficiency sugar beet cultivars. The results indicated that the growth of sugar beet leaves were dramatically restricted, the net photosynthetic rate was significantly decreased, and the energy flux, quantum yield, and flux ratio of PSII reaction centers were adversely affected under B deficiency. Compared to the KWS0143 cultivar, the average leaf area ratio of the KWS1197 cultivar experienced less impact, and its leaf mass ratio (LMR) increased by 26.82% under B deficiency, whereas for the KWS0143 cultivar, the increase was only 2.50%. Meanwhile, the light energy capture and utilization capacity of PSII reaction centers and the proportion of absorbed light energy used for electron transfer were higher by 3.42% under B deficiency; KWS1197 cultivar managed to alleviate the photo-oxidative damage, which results from excessive absorbed energy (ABS/RC), by increasing the dissipated energy (DI_o/RC). Therefore, in response to B deprivation, the KWS1197 cultivar demonstrated greater adaptability in terms of morphological indices and photosynthetic functions, which not only explains the improved performance but also renders the measured parameters as the key features for varietal selection, providing a theoretical basis for the utilization of efficient sugar beet cultivars in future.