Changes in root microbiome during wheat evolution.

BACKGROUND: Although coevolutionary signatures of host-microbe interactions are considered to engineer the healthy microbiome of humans, little is known about the changes in root-microbiome during plant evolution. To understand how the composition of the wheat and its ancestral species microbiome have changed over the evolutionary processes, we performed a 16S rRNA metagenomic analysis on rhizobacterial communities associated with a phylogenetic framework of four Triticum species T. urartu, T. turgidum, T. durum, and T. aestivum along with their ancestral species Aegilops speltoides, and Ae. tauschii during vegetative and reproductive stages. RESULTS: In this study, we illustrated that the genome contents of wild species Aegilops speltoides and Ae. tauschii can be significant factors determining the composition of root-associated bacterial communities in domesticated bread wheat. Although it was found that domestication and modern breeding practices might have had a significant impact on microbiome-plant interactions especially at the reproductive stage, we observed an extensive and selective control by wheat genotypes on associated rhizobacterial communities at the same time. Our data also showed a strong genotypic variation within species of T. aestivum and Ae. tauschii, suggesting potential breeding targets for plants surveyed. CONCLUSIONS: This study performed with different genotypes of Triticum and Aegilops species is the first study showing that the genome contents of Ae. speltoides and Ae. tauschii along with domestication-related changes can be significant factors determining the composition of root-associated bacterial communities in bread wheat. It is also indirect evidence that shows a very extensive range of host traits and genes are probably involved in host-microbe interactions. Therefore, understanding the wheat root-associated microbiome needs to take into consideration of its polygenetic mosaic nature.

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.

DELAY OF GERMINATION 1 (DOG1) regulates dormancy in dimorphic seeds of Xanthium strumarium.

Seed dormancy ensures plant survival but many mechanisms remain unclear. A high-throughput RNA-seq analysis investigated the mechanisms involved in the establishment of dormancy in dimorphic seeds of Xanthium strumarium (L.) developing in one single burr. Results showed that DOG1 , the main dormancy gene in Arabidopsis thaliana L., was over-represented in the dormant seed leading to the formation of two seeds with different cell wall properties. Less expression of DME /EMB1649 , UBP26 , EMF2, MOM, SNL2, and AGO4 in the non-dormant seed was observed, which function in the chromatin remodelling of dormancy-associated genes through DNA methylation. However, higher levels of ATXR7 /SDG25, ELF6 , and JMJ16/PKDM7D in the non-dormant seed that act at the level of histone demethylation and activate germination were found. Dramatically lower expression in the splicing factors SUA, PWI , and FY in non-dormant seed may indicate that variation in RNA splicing for ABA sensitivity and transcriptional elongation control of DOG1 is of importance for inducing seed dormancy. Seed size and germination may be influenced by respiratory factors, and alterations in ABA content and auxin distribution and responses. TOR (a serine/threonine-protein kinase) is likely at the centre of a regulatory hub controlling seed metabolism, maturation, and germination. Over-representation of the respiration-associated genes (ACO3 , PEPC3 , and D2HGDH ) was detected in non-dormant seed, suggesting differential energy supplies in the two seeds. Degradation of ABA biosynthesis and/or proper auxin signalling in the large seed may control germinability, and suppression of endoreduplication in the small seed may be a mechanism for cell differentiation and cell size determination.