Summary Wheat (Triticum aestivum) is one of the most important crops worldwide. Given a growing global population coupled with increasingly challenging cultivation conditions, facilitating wheat breeding by fine‐tuning important traits is of great importance. MADS‐box genes are prime candidates for this, as they are involved in virtually all aspects of plant development. Here, we present a detailed overview of phylogeny and expression of 201 wheat MIKC‐type MADS‐box genes. Homoeolog retention is significantly above the average genome‐wide retention rate for wheat genes, indicating that many MIKC‐type homoeologs are functionally important and not redundant. Gene expression is generally in agreement with the expected subfamily‐specific expression pattern, indicating broad conservation of function of MIKC‐type genes during wheat evolution. We also found extensive expansion of some MIKC‐type subfamilies, especially those potentially involved in adaptation to different environmental conditions like flowering time genes. Duplications are especially prominent in distal telomeric regions. A number of MIKC‐type genes show novel expression patterns and respond, for example, to biotic stress, pointing towards neofunctionalization. We speculate that conserved, duplicated and neofunctionalized MIKC‐type genes may have played an important role in the adaptation of wheat to a diversity of conditions, hence contributing to the importance of wheat as a global staple food.

There are two groups of MADS intervening keratin-like and C-terminal (MIKC)-type MADS box genes, MIKC C type and MIKC* type. In seed plants, the MIKC C type shows considerable diversity, but the MIKC* type has only two subgroups, P-and S-clade, which show conserved expression in the gametophyte. To examine the functional conservation of MIKC*-type genes, we characterized all three rice (Oryza sativa) MIKC*-type genes. All three genes are specifically expressed late in pollen development. The single knockdown or knockout lines, respectively, of the S-clade MADS62 and MADS63 did not show a mutant phenotype, but lines in which both S-clade genes were affected showed severe defects in pollen maturation and germination, as did knockdown lines of MADS68, the only P-clade gene in rice. The rice MIKC*-type proteins form strong heterodimeric complexes solely with partners from the other subclade; these complexes specifically bind to N10-type C-A-rich-G-boxes in vitro and regulate downstream gene expression by binding to N10-type promoter motifs. The rice MIKC* genes have a much lower degree of functional redundancy than the Arabidopsis thaliana MIKC* genes. Nevertheless, our data indicate that the function of heterodimeric MIKC*-type protein complexes in pollen development has been conserved since the divergence of monocots and eudicots, roughly 150 million years ago.

Bsister genes have been identified as the closest relatives of class B floral homeotic genes. Previous studies have shown that Bsister genes from eudicots are involved in cell differentiation during ovule and seed development. However, the complete function of Bsister genes in eudicots is masked by redundancy with other genes and little is known about the function of Bsister genes in monocots, and about the evolution of Bsister gene functions. Here we characterize OsMADS29, one of three MADS-box Bsister genes in rice. Our analyses show that OsMADS29 is expressed in female reproductive organs including the ovule, ovule vasculature, and the whole seed except for the outer layer cells of the pericarp. Knock-down of OsMADS29 by double-stranded RNA-mediated interference (RNAi) results in shriveled and/or aborted seeds. Histological analyses of the abnormal seeds at 7 days after pollination (DAP) indicate that the symplastic continuity, including the ovular vascular trace and the nucellar projection, which is the nutrient source for the filial tissue at early development stages, is affected. Moreover, degeneration of all the maternal tissues in the transgenic seeds, including the pericarp, ovular vascular trace, integuments, nucellar epidermis and nucellar projection, is blocked as compared to control plants. Our results suggest that OsMADS29 has important functions in seed development of rice by regulating cell degeneration of maternal tissues. Our findings provide important insights into the ancestral function of Bsister genes.

MADS-box genes are key regulators of virtually every aspect of plant reproductive development. They play especially prominent roles in flowering time control, inflorescence architecture, floral organ identity determination, and seed development. The developmental and evolutionary importance of MADS-box genes is widely acknowledged. However, their role during flowering plant domestication is less well recognized. Here, we provide an overview illustrating that MADS-box genes have been important targets of selection during crop domestication and improvement. Numerous examples from a diversity of crop plants show that various developmental processes have been shaped by allelic variations in MADS-box genes. We propose that new genomic and genome editing resources provide an excellent starting point for further harnessing the potential of MADS-box genes to improve a variety of reproductive traits in crops. We also suggest that the biophysics of MADS-domain protein-protein and protein-DNA interactions, which is becoming increasingly well characterized, makes them especially suited to exploit coding sequence variations for targeted breeding approaches.

What is the difference between Cannabis, marijuana and hemp?Cannabis is the botanical name of a genus within the Cannabaceae, the same plant family that contains hops. The genus includes three species, C. sativa, C. ruderalis and C. indica. However, the three species interbreed and species boundaries are fl uidtherefore, it has been suggested that only a single Cannabis species, C. sativa, be recognised. One common trait of all Cannabis plants is the presence of secondary compounds called 'cannabinoids', or more precisely 'phytocannabinoids'. There are over 100 different phytocannabinoids, which are predominantly produced in trichomes growing on female Cannabis infl orescences. However, between Cannabis accessions, the profi le and quantity of specifi c phytocannabinoids varies enormously. To refl ect this variation, it has been suggested to classify Cannabis strains according to their chemical phenotypes into 'chemotypes' with distinct cannabinoid profi les.The most famous -or infamouscannabinoid is tetrahydrocannabinol (THC), which is known for its psychotropic effects. The presence of THC is where the difference between 'hemp' and 'marijuana' comes into play. These terms refl ect neither a taxonomic nor a phylogenetic classifi cation, and instead are a refl ection of the plants' cannabinoid profi le and the associated legislative restrictions. Marijuana varieties produce THC as their main cannabinoid, and THC levels can reach up to 20 to 30% of the dry female fl ower mass. However, if the THC content of a plant is below 0.3% of dried fl ower mass (legislation varies from 0.2 to 1% between countries), and its consumption therefore has no hallucinogenic effects, the plant is regarded as hemp.Generally, marijuana strains have higher overall cannabinoid levels and produce a lot of fl owers and side branches, which gives them a bushy appearance. On the other hand, hemp plants usually