HOMEOBOX2, the paralog of SIX-ROWED SPIKE1/HOMEOBOX1, is dispensable for barley spikelet development

The HD-ZIP class I transcription factor Homeobox 1 (HvHOX1), also known as Vulgare Row-type Spike 1 (VRS1) or Six-rowed Spike 1, regulates lateral spikelet fertility in barley (Hordeum vulgare L.). It was shown that HvHOX1 has a high expression only in lateral spikelets, while its paralog HvHOX2 was found to be expressed in different plant organs. Yet, the mechanistic functions of HvHOX1 and HvHOX2 during spikelet development are still fragmentary. Here, we show that compared with HvHOX1, HvHOX2 is more highly conserved across different barley genotypes and Hordeum species, hinting at a possibly vital but still unclarified biological role. Using bimolecular fluorescence complementation, DNA-binding, and transactivation assays, we validate that HvHOX1 and HvHOX2 are bona fide transcriptional activators that may potentially heterodimerize. Accordingly, both genes exhibit similar spatiotemporal expression patterns during spike development and growth, albeit their mRNA levels differ quantitatively. We show that HvHOX1 delays the lateral spikelet meristem differentiation and affects fertility by aborting the reproductive organs. Interestingly, the ancestral relationship of the two genes inferred from their co-expressed gene networks suggested that HvHOX1 and HvHOX2 might play a similar role during barley spikelet development. However, CRISPR-derived mutants of HvHOX1 and HvHOX2 demonstrated the suppressive role of HvHOX1 on lateral spikelets, while the loss of HvHOX2 does not influence spikelet development. Collectively, our study shows that through the suppression of reproductive organs, lateral spikelet fertility is regulated by HvHOX1, whereas HvHOX2 is dispensable for spikelet development in barley

Review: Nutritional ecology of heavy metals

The aim of this review is to focus the attention on the nutrition ecology of the heavy metals and on the major criticisms related to the heavy metals content in animal feeds, manure, soil and animal-origin products. Heavy metals are metallic elements that have a high density that have progressively accumulated in the food chain with negative effects for human health. Some metals are essential (Fe, I, Co, Zn, Cu, Mn, Mo, Se) to maintain various physiological functions and are usually added as nutritional additives in animal feed. Other metals (As, Cd, F, Pb, Hg) have no established biological functions and are considered as contaminants/undesirable substances. The European Union adopted several measures in order to control their presence in the environment, as a result of human activities such as: farming, industry or food processing and storage contamination. The control of the animal input could be an effective strategy to reduce human health risks related to the consumption of animal-origin products and the environmental pollution by manure. Different management of raw materials and feed, animal species as well as different legal limits can influence the spread of heavy metals. To set up effective strategies against heavy metals the complex interrelationships in rural processes, the widely variability of farming practices, the soil and climatic conditions must be considered. Innovative and sustainable approaches have discussed for the heavy metal nutrition ecology to control the environmental pollution from livestock-related activities

Biochemical and molecular characterization of stress-induced β-carbonic anhydrase from a C<SUB>4</SUB> plant, Pennisetum glaucum

Genes encoding for many &#946;-carbonic anhydrases and their functions in various developmental processes are well established in lower plants, however, similar studies are limited in higher plants. We report the cloning and characterization of cDNA encoding for a &#946;-carbonic anhydrase (PgCA) from Pennisetum glaucum, a C4 crop plant. cDNA encoding 249 amino acids and its deduced amino acid sequence analysis revealed that is related to other plant &#946;-CA family members with an over all conserved architecture of a typical &#946;-CA protein. Phylogenetic analysis revealed that PgCA is evolutionarily very close to chloroplast &#946;-CA isoform. Signal sequence predicting programs identify a N-terminus putative chloroplast targeting sequence. Heterologous Escherichia coli expression system was utilized to overexpress recombinant PgCA, which showed high thermostability, an alkaline pH optima and dual activity with both reversible CO2 hydration and esterase activities. The &#946;-CAs studied so far possessed only CO2 hydration activity with no detectable esterase activity. Recombinant PgCA esterase activity is inhibited by standard CA inhibitors acetazolamide, methazolamide and azide. Subcellular immunostaining studies revealed a chloroplastic localization of PgCA protein. Expression of PgCA transcript is differentially up regulated in response to various abiotic stresses wherein its accumulation in Pennisetum leaves positively correlated with the intensity and duration of stress. Biochemical and transcript analyses suggest that PgCA may play a significant role in plant's adaptation to different abiotic stresses in addition to the previously recognized role of replenishing the CO2 supply within plant cells

Genetics of Whole Plant Morphology and Architecture

Plant architectural features directly impact plant fitness and adaptation, and traits related to plant morphology and development represent important targets for crop breeding. Decades of mutagenesis research have provided a wealth of mutant resources, making barley (Hordeum vulgare L.) an interesting model for genetic dissection of grass morphology and architecture. Recent advances in genomics have propelled the identification of barley genes controlling different aspects of shoot and root development. In addition to gene discovery, it is important to understand the interplay between different developmental processes in order to support breeding of improved ideotypes for sustainable barley production under different climatic conditions. The purpose of the present chapter is to: (i) provide an overview of the morphology and development of shoot and root structures in barley; (ii) discuss novel insights into the genetic, molecular and hormonal mechanisms regulating root and shoot development and architecture; and (iii) highlight the genetic and physiological interactions among organs and traits with special focus on correlations between leaf and tiller development, flowering and tillering, as well as row-type and tillering