Excess nitrogen responsive HvMADS27 transcription factor controls barley root architecture by regulating abscisic acid level

Long-Term Study of the Effects of Environment, Variety, and Fertilisation on Yield and Stability of Spring Barley Grain

The stability and yield of barley grain are affected by several factors, such as climatic conditions, fertilisation, and the different barley varieties. In a long-term experiment in Prague, Czech Republic, established in 1955, we analysed the weather trends and how weather, fertilisation (10 treatments in total), and different barley varieties affected grain yield and stability. A total of 44 seasons were evaluated. Trends in mean, minimum, and maximum temperatures from 1953 to 2023, as well as sunshine duration from 1961 to 2022, showed statistically significant increases. The trend for annual precipitation from 1953 to 2023 was not significant, but changes in precipitation were recorded via seasonal precipitation concentration indexes. The unfertilised Control and farmyard manure (FYM) provided the lowest mean yields. Mineral fertilisers (NPK) and FYM+NPK increased grain yield, ranging from 4.9 t ha-1 to 5.5 t ha-1. Three notable correlations between weather conditions and yields were observed: (1) June precipitation (r = 0.4), (2) minimal temperature in July (r = 0.3), and (3) sunshine duration in May (r = -0.5). According to the linear-plateau response model, the reasonable N dose is 55 kg ha-1, resulting in a mean yield of 6.7 t ha-1 for the contemporarily used barley variety Sebastián.

PEP444c encoded within the MIR444c gene regulates microRNA444c accumulation in barley

MicroRNAs are small, noncoding RNA molecules that regulate the expression of their target genes. The MIR444 gene family is present exclusively in monocotyledons, and microRNAs444 from this family have been shown to target certain MADS-box transcription factors in rice and barley. We identified three barley MIR444 (MIR444a/b/c) genes and comprehensively characterised their structure and the processing pattern of the primary transcripts (pri-miRNAs444). Pri-microRNAs444 undergo extensive alternative splicing, generating functional and nonfunctional pri-miRNA444 isoforms. We show that barley pri-miRNAs444 contain numerous open reading frames (ORFs) whose transcripts associate with ribosomes. Using specific antibodies, we provide evidence that selected ORFs encoding PEP444a within MIR444a and PEP444c within MIR444c are expressed in barley plants. Moreover, we demonstrate that CRISPR-associated endonuclease 9 (Cas9)-mediated mutagenesis of the PEP444c-encoding sequence results in a decreased level of PEP444 transcript in barley shoots and roots and a 5-fold reduced level of mature microRNA444c in roots. Our observations suggest that PEP444c encoded by the MIR444c gene is involved in microRNA444c biogenesis in barley.

MicroRNA172b-5p/trehalose-6-phosphate synthase module stimulates trehalose synthesis and microRNA172b-3p/AP2-like module accelerates flowering in barley upon drought stress

MicroRNAs (miRNAs) are major regulators of gene expression during plant development under normal and stress conditions. In this study, we analyzed the expression of 150 conserved miRNAs during drought stress applied to barley ready to flower. The dynamics of miRNAs expression was also observed after rewatering. Target messenger RNA (mRNAs) were experimentally identified for all but two analyzed miRNAs, and 41 of the targets were not reported before. Drought stress applied to barley induced accelerated flowering coordinated by a pair of two differently expressed miRNAs originating from a single precursor: hvu-miR172b-3p and hvu-miR172b-5p. Increased expression of miRNA172b-3p during drought leads to the downregulation of four APETALA2(AP2)-like genes by their mRNA cleavage. In parallel, the downregulation of the miRNA172b-5p level results in an increased level of a newly identified target, trehalose-6-phosphate synthase, a key enzyme in the trehalose biosynthesis pathway. Therefore, drought-treated plants have higher trehalose content, a known osmoprotectant, whose level is rapidly dropping after watering. In addition, trehalose-6-phosphate, an intermediate of the trehalose synthesis pathway, is known to induce flowering. The hvu-miRNA172b-5p/trehalose-6-phosphate synthase and hvu-miRNA172b-3p/AP2-like create a module leading to osmoprotection and accelerated flowering induction during drought.

Recent Insights into Plant miRNA Biogenesis: Multiple Layers of miRNA Level Regulation

MicroRNAs are small RNAs, 20-22 nt long, the main role of which is to downregulate gene expression at the level of mRNAs. MiRNAs are fundamental regulators of plant growth and development in response to internal signals as well as in response to abiotic and biotic factors. Therefore, the deficiency or excess of individual miRNAs is detrimental to particular aspects of a plant's life. In consequence, the miRNA levels must be appropriately adjusted. To obtain proper expression of each miRNA, their biogenesis is controlled at multiple regulatory layers. Here, we addressed processes discovered to influence miRNA steady-state levels, such as MIR transcription, co-transcriptional pri-miRNA processing (including splicing, polyadenylation, microprocessor assembly and activity) and miRNA-encoded peptides synthesis. MiRNA stability, RISC formation and miRNA export out of the nucleus and out of the plant cell also define the levels of miRNAs in various plant tissues. Moreover, we show the evolutionary conservation of miRNA biogenesis core proteins across the plant kingdom.