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Summary: The AGAMOUS‐LIKE6 (AGL6)‐like genes are ancient MADS‐box genes and are functionally studied in a few model plants. The knowledge of these genes in wheat remains limited. Here, by studying a 'double homoeolog mutant' of the AGL6 gene in tetraploid wheat, we showed that AGL6 was required for the development of all four whorls of floral organs with dosage‐dependent effect on floret fertility. Yeast two‐hybrid analyses detected interactions of AGL6 with all classes of MADS‐box proteins in the ABCDE model for floral organ development. AGL6 was found to interact with several additional proteins, including the G protein β and γ (DEP1) subunits. Analysis of the DEP1‐B mutant showed a significant reduction in spikelet number per spike in tetraploid wheat, while overexpression of AGL6 in common wheat increased the spikelet number per spike and hence the grain number per spike. RNA‐seq analysis identified the regulation of several meristem activity genes by AGL6, such as FUL2 and TaMADS55. Our work therefore extensively updated the wheat ABCDE model and proposed an alternative approach to improve wheat grain yield by manipulating the AGL6 gene. [ABSTRACT FROM AUTHOR]

Summary: The wheat AP2‐like transcription factor gene Q has played a major role in domestication by conferring the free‐threshing character and pleiotropically affecting numerous other traits. However, little information is known regarding the molecular mechanisms associated with the regulation of these traits by Q, especially for the structural determination of threshability. Here, transcriptome analysis of immature spike tissues in three lines nearly isogenic for Q revealed over 3000 differentially expressed genes (DEGs) involved in a number of pathways. Using phenotypic, microscopic, transcriptomic, and tissue‐specific gene expression analyses, we demonstrated that Q governs threshability through extensive modification of wheat glumes including their structure, cell wall thickness, and chemical composition. Critical DEGs and pathways involved in secondary cell wall synthesis and regulation of the chemical composition of glumes were identified. We also showed that the mutation giving rise to the Q allele synchronized the expression of genes for micro‐sporogenesis that affected pollen fertility, and may determine the final grain number for wheat spikes. Transcriptome dissection of genes and genetic pathways regulated by Q should further our understanding of wheat domestication and improvement. Significance Statement: The Q gene has played a major role in the domestication of wheat, and contributed to the rise of modern human civilization. The knowledge gained in this study regarding the genes, pathways, and physiological mechanisms underpinning seed threshability and pollen fertility, two important traits pleiotropically regulated by Q, provides a better understanding of wheat domestication and improvement. [ABSTRACT FROM AUTHOR]

SQUAMOSA Promoter-Binding Protein-Like (SPL) genes encode plantspecific transcription factors that play important roles in plant phase transition, flower and fruit development, plant architecture, gibberellins signaling, sporogenesis, and response to copper and fungal toxins. In Arabidopsis, many SPL genes are post-transcriptionally regulated by the microRNA (miRNA) miR156, among which AtSPL9 in turn positively regulates the expression of the second miRNA miR172. This miR156- AtSPL9-miR172 regulatory pathway plays critical roles during juvenile to adult leaf development and the miR156-SPLs feedback interaction persists all through the plant development, which may be conserved in other plants. In the present paper, we provide a concise review on the most recent progress in the regulatorymechanisms associated with plant SPL transcription factors, especially in relation to miRNAs. The potential application of these discoveries in agriculture is briefly discussed. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are important post-transcriptional regulators of their target genes in plants and animals. miRNAs are usually 20-24 nucleotides long. Despite their unusually small sizes, the evolutionary history of miRNA gene families seems to be similar to their protein-coding counterparts. In contrast to the small but abundant miRNA families in the animal genomes, plants have fewer but larger miRNA gene families. Members of plant miRNA gene families are often highly similar, suggesting recent expansion via tandem gene duplication and segmental duplication events. Although many miRNA genes are conserved across plant species, the same gene family varies significantly in size and genomic organization in different species, which may cause dosage effects and spatial and temporal differences in target gene regulations. In this review, we summarize the current progress in understanding the evolution of plant miRNA gene families.Cell Research (2007) 17: 212–218. doi: 10.1038/sj.cr.7310113; published online 28 November 2006 [ABSTRACT FROM AUTHOR]

Abstract: Populus trichocarpa (poplar) is distinguished from its herbaceous counterparts Arabidopsis and rice by its woody structure, perennial life cycle, and dioecious, two-whorled flowers. MADS-box genes are known to be involved in many important processes during plant development. Investigation of the poplar genome revealed 105 putative functional MADS-box genes and 12 pseudogenes. These numbers are comparable to those in Arabidopsis. However, poplar has 64 type II MADS-box genes, implying a higher birth rate when compared with Arabidopsis (64 vs.47). In addition to duplications for floral organ identity genes, TM3-like, StMADS11, ANR1 and Bs clades were significantly increased. As indicated by the phylogenetic analysis, there exist at least two MIKC⁎ MADS-box genes in the poplar genome. In contrast, only 41 putative functional type I genes and 9 pseudogenes were found, suggesting that the poplar type I MADS-box genes have experienced a lower rate in both birth and death. Poplar MADS-box genes were distributed on all linkage groups (LGs), except LG XIX. Like other gene families, poplar MADS-box gene family has expanded through tandem gene duplication and segmental duplication events as demonstrated by two genomic regions where clustered MADS-box genes exhibited high similarities in the MADS-box domains. A survey of poplar EST sequences showed that MADS-box genes were expressed in wood and cambium tissues, which are specific to woody plants. The expression of common MADS-box gene in tree-specific tissues suggests that the novel function combinations of a set of genes similar to those in herbaceous plants may account for the development of woody characteristics in poplar. [Copyright &y& Elsevier]