Induced secretion system mutation alters rhizosphere bacterial composition in Sorghum bicolor (L.) Moench

Harnessing root-soil-microbiota interactions for drought-resilient cereals

Cereal plants form complex networks with their associated microbiome in the soil environment. A complex system including variations of numerous parameters of soil properties and host traits shapes the dynamics of cereal microbiota under drought. These multifaceted interactions can greatly affect carbon and nutrient cycling in soil and offer the potential to increase plant growth and fitness under drought conditions. Despite growing recognition of the importance of plant microbiota to agroecosystem functioning, harnessing the cereal root microbiota remains a significant challenge due to interacting and synergistic effects between root traits, soil properties, agricultural practices, and drought-related features. A better mechanistic understanding of root-soil-microbiota associations could lead to the development of novel strategies to improve cereal production under drought. In this review, we discuss the root-soil-microbiota interactions for improving the soil environment and host fitness under drought and suggest a roadmap for harnessing the benefits of these interactions for drought-resilient cereals. These methods include conservative trait-based approaches for the selection and breeding of plant genetic resources and manipulation of the soil environments.

A large sequenced mutant library - valuable reverse genetic resource that covers 98% of sorghum genes

Mutant populations are crucial for functional genomics and discovering novel traits for crop breeding. Sorghum, a drought and heat-tolerant C4 species, requires a vast, large-scale, annotated, and sequenced mutant resource to enhance crop improvement through functional genomics research. Here, we report a sorghum large-scale sequenced mutant population with 9.5 million ethyl methane sulfonate (EMS)-induced mutations that covered 98% of sorghum's annotated genes using inbred line BTx623. Remarkably, a total of 610 320 mutations within the promoter and enhancer regions of 18 000 and 11 790 genes, respectively, can be leveraged for novel research of cis-regulatory elements. A comparison of the distribution of mutations in the large-scale mutant library and sorghum association panel (SAP) provides insights into the influence of selection. EMS-induced mutations appeared to be random across different regions of the genome without significant enrichment in different sections of a gene, including the 5' UTR, gene body, and 3'-UTR. In contrast, there were low variation density in the coding and UTR regions in the SAP. Based on the Ka /Ks value, the mutant library (~1) experienced little selection, unlike the SAP (0.40), which has been strongly selected through breeding. All mutation data are publicly searchable through SorbMutDB (https://www.depts.ttu.edu/igcast/sorbmutdb.php) and SorghumBase (https://sorghumbase.org/). This current large-scale sequence-indexed sorghum mutant population is a crucial resource that enriched the sorghum gene pool with novel diversity and a highly valuable tool for the Poaceae family, that will advance plant biology research and crop breeding.

Inoculation of wheat with Bacillus sp. wp-6 altered amino acid and flavonoid metabolism and promoted plant growth

Inoculation of wheat seedling with Bacillus sp. wp-6 changed amino acid metabolism and flavonoid synthesis and promoted plant growth. Plant growth-promoting rhizobacteria (PGPR), which can reduce the use of agrochemicals, is vital for the development of sustainable agriculture. In this study, proteomics and metabolomics analyses were performed to investigate the effects of inoculation with a PGPR, Bacillus sp. wp-6, on wheat (Triticum aestivum L.) seedling growth. The results showed that inoculation with Bacillus sp. wp-6 increased shoot and root fresh weights by 19% and 18%, respectively, after 40 days. The expression levels of alpha-linolenic acid metabolism-related proteins and metabolites (lipoxygenase 2, allene oxide synthase 2, jasmonic acid, 17-hydroxylinolenic acid) and flavonoid biosynthesis-related proteins and metabolites (chalcone synthase 2 and PHC 4'-O-glucoside) were up-regulated. In addition, the expression levels of amino acid metabolism-related proteins (NADH-dependent glutamate synthase, bifunctional aspartokinase/homoserine, anthranilate synthase alpha subunit 1, and 3-phosphoshikimate 1-carboxyvinyltransferase) and metabolites (L-aspartate, L-arginine, and S-glutathionyl-L-cysteine) were also significantly up-regulated. Among them, NADH-dependent glutamate synthase and bifunctional aspartokinase/homoserine could act as regulators of nitrogen metabolism. Overall, inoculation of wheat with Bacillus sp. wp-6 altered alpha-linolenic acid metabolism, amino acid metabolism, and flavonoid synthesis and promoted wheat seedling growth. This study will deepen our understanding of the mechanism by which Bacillus sp. wp-6 promotes wheat growth using proteomics and metabolomics.