•Wheat is the most widely grown crop globally, providing 20 % of all human calories and protein. Achieving step changes in genetic yield potential is crucial to ensure food security, but efforts are thwarted by an apparent trade-off between grain size and number. Expansins are proteins that play important roles in plant growth by enhancing stress relaxation in the cell wall, which constrains cell expansion. •Here, we describe how targeted over-expression of an α-expansin in early developing wheat seeds leads to a significant increase in grain size without a negative effect on grain number, resulting in a yield boost under field conditions. •The best-performing transgenic line yielded 12.3 % higher average grain weight than the control, and this translated to an increase in grain yield of 11.3 % in field experiments using an agronomically appropriate plant density. •This targeted transgenic approach provides an opportunity to overcome a common bottleneck to yield improvement across many crops.

Sulfur is an essential nutrient for plant growth and development. Sulfur is a constituent of proteins, the plasma membrane and cell walls, among other important cellular components. To obtain new insights into the gene regulatory networks underlying the sulfate response, we performed an integrative meta-analysis of transcriptomic data from five different sulfate experiments available in public databases. This bioinformatic approach allowed us to identify a robust set of genes whose expression depends only on sulfate availability, indicating that those genes play an important role in the sulfate response. In relation to sulfate metabolism, the biological function of approximately 45% of these genes is currently unknown. Moreover, we found several consistent Gene Ontology terms related to biological processes that have not been extensively studied in the context of the sulfate response; these processes include cell wall organization, carbohydrate metabolism, nitrogen compound transport, and the regulation of proteolysis. Gene co-expression network analyses revealed relationships between the sulfate-responsive genes that were distributed among seven function-specific co-expression modules. The most connected genes in the sulfate co-expression network belong to a module related to the carbon response, suggesting that this biological function plays an important role in the control of the sulfate response. Temporal analyses of the network suggest that sulfate starvation generates a biphasic response, which involves that major changes in gene expression occur during both the early and late responses. Network analyses predicted that the sulfate response is regulated by a limited number of transcription factors, including MYBs, bZIPs, and NF-YAs. In conclusion, our analysis identified new candidate genes and provided new hypotheses to advance our understanding of the transcriptional regulation of sulfate metabolism in plants.

LSU proteins belong to a plant-specific gene family initially characterized by their strong induction in response to sulfate (S) deficiency. In the last few years, LSUs have arisen as relevant hubs in protein–protein interaction networks, in which they play relevant roles in the response to abiotic and biotic stresses. Most of our knowledge on LSU genomic organization, expression and function comes from studies in Arabidopsis and tobacco, while little is known about the LSU gene repertoire and evolution of this family in land plants. In this work, a total of 270 LSU family members were identified using 134 land plant species with whole-genome sequences available. Phylogenetic analysis revealed that LSU genes belong to a Spermatophyta-specific gene family, and their homologs are distributed in three major groups, two for dicotyledons and one group for monocotyledons. Protein sequence analyses showed four new motifs that further support the subgroup classification by phylogenetic analyses. Moreover, we analyzed the expression of LSU genes in one representative species of each phylogenetic group (wheat, tomato and Arabidopsis) and found a conserved response to S deficiency, suggesting that these genes might play a key role in S stress responses. In summary, our results indicate that LSU genes belong to the Spermatophyta-specific gene family and their response to S deficiency is conserved in angiosperms.