Polyploidy, the presence of more than two complete sets of chromosomes in an organism, has significantly shaped the genomes of angiosperms during evolution. Two forms of polyploidy are often considered: allopolyploidy, which originates from interspecies hybrids, and autopolyploidy, which originates from intraspecies genome duplication events. Besides affecting genome organization, polyploidy generates other genetic effects. Synthetic allopolyploid plants exhibit considerable transcriptome alterations, part of which are likely caused by the reunion of previously diverged regulatory hierarchies. In contrast, autopolyploids have relatively uniform genomes, suggesting lower alteration of gene expression. To evaluate the impact of intraspecies genome duplication on the transcriptome, we generated a series of unique Arabidopsis thaliana autotetraploids by using different ecotypes. A. thaliana autotetraploids show transcriptome alterations that strongly depend on their parental genome composition and include changed expression of both new genes and gene groups previously described from allopolyploid Arabidopsis . Alterations in gene expression are stable, nonstochastic, developmentally specific, and associated with changes in DNA methylation. We propose that Arabidopsis possesses an inherent and heritable ability to sense and respond to elevated, yet balanced chromosome numbers. The impact of natural variation on alteration of autotetraploid gene expression stresses its potential importance in the evolution and breeding of plants.

Deficiency of the essential nutrient boron (B) in the soil is one of the most widespread micronutrient deficiencies worldwide, leading to developmental defects in root and shoot tissues of plants, and severe yield reductions in many crops. Despite this agricultural importance, the underlying mechanisms of how B shapes plant developmental and morphological processes are still not unequivocally understood in detail. This review evaluates experimental approaches that address our current understanding of how B influences plant morphological processes by focusing on developmental defects observed under B deficiency. We assess what is known about mechanisms that control B homeostasis and specifically highlight: (i) limitations in the methodology that is used to induce B deficiency; (ii) differences between mutant phenotypes and normal plants grown under B deficiency; and (iii) recent research on analyzing interactions between B and phytohormones. Our analysis highlights the need for standardized methodology to evaluate the roles of B in the cell wall versus other parts of the cell.

Boron deficiency is an abiotic stress that negatively impacts plant growth and yield worldwide. Boron deficiency primarily affects the development of plant meristems— stem cells critical for all post-embryonic tissue growth. The essential role of boron in meristem development was first established in 1923. It remains unclear whether boron directly integrates into meristem molecular signalling pathways. In addition to its stabilizing function in the primary cell wall, growing evidence suggests roles for boron in various molecular processes including phytohormone cascades. These indications enhance a mechanistic understanding of why boron is crucial for proper meristem development. In this review we compile and discuss molecular pathways influenced by boron availability in Arabidopsis (Arabidopsis thaliana), maize (Zea mays), rice (Oryza sativa), and oilseed rape (Brassica napus) with a focus on the auxin-, ethylene-, and cytokinin-mediated hormone cascades. We particularly compare and contrast phenotypic and molecular adaptations of shoot and root meristems to boron deficiency and pinpoint tissue-specific differences.

Boron (B) is an essential micronutrient for organisms. In plants, B is known to stabilize the cell wall by crosslinking Rhamnogalacturonan II through ester bonds formed with cis-diols of sugar moieties. However, B is believed to be required for additional functions such as stability and function of (plasma membrane) proteins involved in signal transduction pathways. We have recently shown that boronic acids, competitors of B, efficiently induce perfect phenocopies of monopteros mutants. This effect is enigmatic because like B, boronic acids should find numerous cellular targets and thus disturb many biologic processes ending in a spectrum of unspecific embryo phenotypes. Based on chemical characteristics of boronic acids and their derivatives we discuss reasons that could explain this unusual specificity. The peculiarities of this class of compounds could provide new tools for studying developmental processes.