Arabidopsis HEAT SHOCK TRANSCRIPTION FACTORA1b regulates multiple developmental genes under benign and stress conditions.

In Arabidopsis thaliana, HEAT SHOCK TRANSCRIPTION FACTORA1b (HSFA1b) controls resistance to environmental stress and is a determinant of reproductive fitness by influencing seed yield. To understand how HSFA1b achieves this, we surveyed its genome-wide targets (ChIP-seq) and its impact on the transcriptome (RNA-seq) under non-stress (NS), heat stress (HS) in the wild type, and in HSFA1b-overexpressing plants under NS. A total of 952 differentially expressed HSFA1b-targeted genes were identified, of which at least 85 are development associated and were bound predominantly under NS. A further 1780 genes were differentially expressed but not bound by HSFA1b, of which 281 were classified as having development-associated functions. These genes are indirectly regulated through a hierarchical network of 27 transcription factors (TFs). Furthermore, we identified 480 natural antisense non-coding RNA (cis NAT) genes bound by HSFA1b, defining a further mode of indirect regulation. Finally, HSFA1b-targeted genomic features not only harboured heat shock elements, but also MADS box, LEAFY, and G-Box promoter motifs. This revealed that HSFA1b is one of eight TFs that target a common group of stress defence and developmental genes. We propose that HSFA1b transduces environmental cues to many stress tolerance and developmental genes to allow plants to adjust their growth and development continually in a varying environment.

Journal of Experimental Botany 2018, 69(11):2847–2862

DOI: 10.1093/jxb/ery142

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MicroRNAs (miRNAs) and Plant Development

Development in plants is a continuous process during which new tissues and organs are formed all along its life cycle. Development involves the coordination of both time and space of complex cellular processes such as proliferation, expansion and differentiation following endogenous programmes and in response to environmental signals. Since their discovery in 2002, plant microRNAs (miRNAs), a class of small single-stranded regulatory ribonucleic acids (RNAs) have emerged as important nodes in regulatory networks controlling plant development. For instance, miRNAs play important roles for cell fate determination during the patterning of organs and contribute to the regulation of their growth. In addition, miRNAs integrate different signals to regulate the life cycle of plants. Finally, miRNAs appear as molecular links between environmental signals and plant development and may constitute levers to modify plant development in crops.

Key Concepts

  • miRNAs are essential for plant development as mutants affecting miRNA biogenesis or function are embryo lethal or show severe pleiotropic defects.
  • miRNA precursors are mostly produced from independent genetic units and are processed into mature miRNAs via a complex core machinery.
  • miRNAs can have different effects on the expression of their target genes, controlling their spatial pattern, their level of expression or the timing of their expression.
  • miRNAs are regulating many different developmental processes, including pattern formation, morphogenesis and differentiation at all stages of a plant's life.
  • Most of the miRNAs regulating plant development are evolutionary conserved and target evolutionary conserved transcription factors.
  • miRNAs can act non-cell-autonomously, generating a mobile signal that contributes to pattern formation through the regulation of the expression pattern of their targets.
  • miRNAs are integrated into complex regulatory networks and their expression is regulated by both endogenous and exogenous signals.

In: eLS. John Wiley & Sons, Ltd: Chichester.

DOI: 10.1002/9780470015902.a0020106.pub2

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