The mechanism of phosphate (Pi)-mediated salt tolerance in maize is poorly understood. In this study, the effects of Pi (H₂PO₄⁻) on the salt tolerance of two contrasting genotypes was investigated in a pot experiment. We discovered that the application of 3 mM Pi could alleviate salt injury caused by 200 mM NaCl. High amounts of compatible solutes and low amounts of reactive oxygen species (ROS) were also observed under Pi application. Consistent with the increased tolerance, the total number of roots and the growth of shoots increased to relieve salt stress. This phenomenon could be associated with the observed increased expression of nitrate transporters. Furthermore, the seedlings presented a negative relationship between sodium (Na⁺) and Pi (low Na⁺ content and high Pi content), which is related to the genes ZmNHX1, ZmPHT1;8, and ZmPHT1;9, indicating that the exclusion of Na⁺ was promoted by high Pi uptake. However, high Na⁺ and low potassium (K⁺) efflux were detected in the roots, and these were positively correlated with two K⁺ transporters. These observations indicate that Na⁺ exclusion was directly induced by high K⁺ retention rather than Pi absorption. We conclude that maize salt tolerance increased in response to Pi application by promoting Na⁺ exclusion.

Maize, as a glycophyte, is hypersensitive to salinity, but the salt response mechanism of maize remains unclear. In this study, the physiological, biochemical, and molecular responses of two contrasting inbred lines, the salt-tolerant QXH0121 and salt-sensitive QXN233 lines, were investigated in response to salt stress. Under salt stress, the tolerant QXH0121 line exhibited good performance, while in the sensitive QXN233 line, there were negative effects on the growth of the leaves and roots. The most important finding was that QXH0121 could reshift Na⁺ from shoots into long roots, migrate excess Na⁺ in shoots to alleviate salt damage to shoots, and also improve K⁺ retention in shoots, which were closely associated with the enhanced expression levels of ZmHAK1 and ZmNHX1 in QXH0121 compared to those in QXN233 under salt stress. Additionally, QXH0121 leaves accumulated more proline, soluble protein, and sugar contents and had higher SOD activity levels than those observed in QXN233, which correlated with the upregulation of ZmP5CR, ZmBADH, ZmTPS1, and ZmSOD4 in QXH0121 leaves. These were the main causes of the higher salt tolerance of QXH0121 in contrast to QXN233. These results broaden our knowledge about the underlying mechanism of salt tolerance in different maize varieties, providing novel insights into breeding maize with a high level of salt resistance.

Microbial contamination causes serious damage in plant tissue culture, and attention is always being paid regarding how to control and prevent the unwanted pollution. Dwarf hygro (Hygrophila polysperma) is a popular ornamental aquatic plant and its tissue culture has been reported, but the microbial pollution and the cure of microbial pollution was unknown. In this study, a number of bacteria and fungi were isolated from contaminants in MS culture media. Based on the 16S rDNA and ITS sequencing, it was identified that fifteen bacteria belong to Bacillus, Enterobacter, Pantoea, Kosakonia, Ensifer and Klebsiella, and three fungi belong to Plectosphaerella, Cladosporium and Peniophora, respectively. In addition, some drugs were further tested to be free of the bacteria and fungi pollution. The results revealed that 10 μg/mL of kanamycin, 5 μg/mL of chloramphenicol, and 0.015625% potassium sorbate could be applied jointly in MS media to prevent the microbial pollution, and the survival rate of H. polysperma explants was highly improved. This study reveals the bacteria and fungi species from the culture pollution of H. polysperma and provides a practical reference for optimizing the tissue culture media for other aquatic plants.

The barbel chub (Squaliobarbus curriculus), the only species in the genus, is widely distributed in freshwater lakes and rivers at different latitudes in East Asia, with fishery and biodiversity importance, and is an emerging commercially important fish in China. However, the resource of this species has dramatically declined due to anthropogenic activities such as over-exploitation, as well as water pollution. Genomic resources for S. curriculus are useful for the management and sustainable utilization of this important fish species, and also for a better understanding of its genetic variation in the region. Here, we report the chromosome-level assembly of the S. curriculus genome obtained from the integration of PacBio long sequencing and Hi-C technology. A total of 155.34 Gb high-quality PacBio sequences were generated, and the preliminary genome assembly was 894.95 Mb in size with a contig N50 being 20.34 Mb. By using Hi-C data, 99.42% of the assembled sequences were anchored to 24 pseudochromosomes, with chromosome lengths ranging from 27.22 to 58.75 Mb. A total of 25,779 protein-coding genes were predicted, 94.70% of which were functionally annotated. Moreover, S. curriculus shows resistance to grass carp haemorrhagic disease (GCHD) caused by grass carp reovirus (GCRV), which seriously hinders the status and future perspectives of commercial grass carp production. Phylogenetic analysis indicated that S. curriculus diverged with grass carp (Ctenopharyngodon idellus) approximately 20.80 million years ago. Annotations of the expanded gene families were found to be largely enriched in immune-related KEGG pathway categories. Moreover, a total of 18 Toll-like receptor (TLR) genes were identified from the whole genome of S. curriculus. The high-quality genome assembled in this study will provide a valuable resource for accelerating ecological, evolutionary, and genetic research on S. curriculus.