Optimizing cytokinin distribution patterns is a promising strategy for simultaneously enhancing grain yield, grain quality, and stress resistance in plants, as

Brassinosteroids (BRs) regulate various agronomic traits such as plant height, leaf angle, and grain size in rice (Oryza sativa L.); thus, BR signaling components are promising targets for molecular rational design. However, genetic materials for BR-signaling genes or family members remain limited in rice. Here, by genome editing using clustered regularly interspaced short palindromic repeats (CRSPR)/Cas9 tools, we generated a panel of single, double, triple, or quadruple mutants within three BR signaling gene families, including GSK3/SHAGGY-LIKE KINASE1 (GSK1)–GSK4, BRASSINAZOLE-RESISTANT1 (OsBZR1)–OsBZR4, and protein phosphatases with kelch-like (PPKL)1–PPKL3, under the same background (Zhonghua11, japonica). The high-order mutants were produced by either simultaneously targeting multiple sites on different genes of one family (GSKs and PPKLs) or targeting the overlapping sequences of family members (OsBZRs). The mutants exhibited a diversity of plant height, leaf angle, and grain morphology. Comparison analysis of the phenotypes together with BR sensitivity tests suggested the existence of functional redundancy, differentiation, or dominancy among the members within each family. In addition, we generated a set of transgenic plants overexpressing GSK2, OsBZR1/2, and PPKL2, respectively, in wild-type or activated forms with fusion of different tags, and also verified the protein response to BR application. Collectively, these plants greatly enriched the diversity of important agronomic traits in rice. We propose that editing of BR-related family genes could be a feasible approach for screening of desired plants to meet different requirements. Release of these materials as well as the related information also provides valuable resources for further BR research and utilization.

The homeodomain-leucine zipper (HD-Zip) gene family, a group of plant-specific transcriptional factors (TFs), participates in regulating growth, development, and environmental responses. However, the characteristics and biological functions of HD-Zip genes in Prunus mume, which blooms in late winter or early spring, have not been reported. In this study, 32 HD-Zip genes, named PmHB1–PmHB32 based on their chromosomal positions, were identified in the genome of P. mume. These genes are distributed among seven chromosomes and are phylogenetically clustered into four major groups. Gene structure and motif composition were mostly conserved in each group. The Ka/Ks ratios showed that purifying selection has played a leading role in the long-term evolution of the genes, which maintained the function of this family. MicroRNA target site prediction indicated that the genes of the HD-Zip III subfamily may be regulated by miR165/166. Expression pattern analysis showed that the 32 genes were differentially expressed across five different tissues (leaf, flower bud, stem, fruit, and root) and at different stages of stem and leaf-bud development, suggesting that 10 of the genes may play important roles in stem development. Protein–protein interaction predictions showed that the subfamily III genes may regulate vascular development and shoot apical meristem (SAM) maintenance. Promoter analysis showed that the HD-Zip III genes might be involved in responses to light, hormones, and abiotic stressors and stem development. Taken together, our results provide an overview of the HD-Zip family in P. mume and lay the foundation for the molecular breeding of woody ornamental plants.

Japonica/geng and indica/xian are two major rice (Oryza sativa) subspecies with multiple divergent traits, but how these traits are related and interact within each subspecies remains elusive. Brassinosteroids (BRs) are a class of steroid phytohormones that modulate many important agronomic traits in rice. Here, using different physiological assays, we revealed that japonica rice exhibits an overall lower BR sensitivity than indica. Extensive screening of BR signaling genes led to the identification of a set of genes distributed throughout the primary BR signaling pathway with divergent polymorphisms. Among these, we demonstrate that the C38/T variant in BR Signaling Kinase2 (OsBSK2), causing the amino acid change P13L, plays a central role in mediating differential BR signaling in japonica and indica rice. OsBSK2^L13 in indica plays a greater role in BR signaling than OsBSK2^P13 in japonica by affecting the auto‐binding and protein accumulation of OsBSK2. Finally, we determined that OsBSK2 is involved in a number of divergent traits in japonica relative to indica rice, including grain shape, tiller number, cold adaptation, and nitrogen‐use efficiency. Our study suggests that the natural variation in OsBSK2 plays a key role in the divergence of BR signaling, which underlies multiple divergent traits between japonica and indica.

Two ABCG transporters in Medicago truncatula collaboratively regulate flower cuticle secretion and control stigma exsertion by affecting physical contact betwee

Alfalfa (Medicago sativa L.) is an important forage crop worldwide, but molecular genetics and breeding research in this species are hindered by its self-incompatibility (SI). Although the mechanisms underlying SI have been extensively studied in other plant families, SI in legumes, including alfalfa, remains poorly understood. Here, we determined that self-pollinated pollen tubes could germinate on the stigma of alfalfa, grow through the style, and reach the ovarian cavity, but the ovules collapsed ~48 h after self-pollination. A transcriptomic analysis of dissected pistils 24 h after self-pollination identified 941 differently expressed genes (DEGs), including 784 upregulated and 157 downregulated genes. A gene ontology (GO) analysis showed that the DEGs were highly enriched in functions associated with the regulation of pollen tube growth and pollen germination. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that pentose and glucuronate interconversion, plant hormone signal transduction, the spliceosome, and ribosomes might play important roles in SI. Our co-expression analysis showed that F-box proteins, serine/threonine protein kinases, calcium-dependent protein kinases (CDPKs), bHLHs, bZIPs, and MYB-related family proteins were likely involved in the SI response. Our study provides a catalog of candidate genes for further study to understand SI in alfalfa and related legumes.