Translational research in agricultural biology-enhancing crop resistivity against environmental stress alongside nutritional quality

Cell-penetrating peptides for sustainable agriculture

Cell-penetrating peptides (CPPs) are short (typically 5-30 amino acids), cationic, amphipathic, or hydrophobic peptides that facilitate the cellular uptake of diverse cargo molecules by eukaryotic cells via direct translocation or endocytosis across the plasma membrane. CPPs can deliver a variety of bioactive cargos, including proteins, peptides, nucleic acids, and small molecules into the cell. Once inside, the delivered cargo may function in the cytosol, nucleus, or other subcellular compartments. Numerous CPPs have been used for studies and drug delivery in mammalian systems. Although CPPs have many potential uses in plant research and agriculture, the application of CPPs in plants remains limited. Here we review the structures and mechanisms of CPPs and highlight their potential applications for sustainable agriculture.

Molecular Insight of Plants Response to Drought Stress: Perspectives and New Insights towards Food Security

In the face of climate-induced challenges, understanding the intricate molecular mechanisms underlying drought tolerance in plants has become imperative [...].

Unraveling the genetics of polyamine metabolism in barley for senescence-related crop improvement

We explored the polyamine (PA) metabolic pathway genes in barley (Hv) to understand plant development and stress adaptation in Gramineae crops with emphasis on leaf senescence. Bioinformatics and functional genomics tools were utilized for genome-wide identification, comprehensive gene features, evolution, development and stress effects on the expression of the polyamine metabolic pathway gene families (PMGs). Three S-adenosylmethionine decarboxylases (HvSAMDCs), two ornithine decarboxylases (HvODCs), one arginine decarboxylase (HvADC), one spermidine synthase (HvSPDS), two spermine synthases (HvSPMSs), five copper amine oxidases (HvCuAOs) and seven polyamine oxidases (HvPAOs) members of PMGs were identified and characterized in barley. All the HvPMG genes were found to be distributed on all chromosomes of barley. The phylogenetic and comparative assessment revealed that PA metabolic pathway is highly conserved in plants and the prediction of nine H. vulgare miRNAs (hvu-miR) target sites, 18 protein-protein interactions and 961 putative CREs in the promoter region were discerned. Gene expression of HvSAMDC3, HvCuAO7, HvPAO4 and HvSPMS1 was apparent at every developmental stage. SPDS/SPMS gene family was found to be the most responsive to induced leaf senescence. This study provides a reference for the functional investigation of the molecular mechanism(s) that regulate polyamine metabolism in plants as a tool for future breeding decision management systems.

Polyamines and Their Biosynthesis/Catabolism Genes Are Differentially Modulated in Response to Heat Versus Cold Stress in Tomato Leaves (Solanum lycopersicum L.)

Polyamines (PAs) regulate growth in plants and modulate the whole plant life cycle. They have been associated with different abiotic and biotic stresses, but little is known about the molecular regulation involved. We quantified gene expression of PA anabolic and catabolic pathway enzymes in tomato (Solanum lycopersicum cv. Ailsa Craig) leaves under heat versus cold stress. These include arginase1 and 2, arginine decarboxylase 1 and 2, agmatine iminohydrolase/deiminase 1, N-carbamoyl putrescine amidase, two ornithine decarboxylases, three S-adenosylmethionine decarboxylases, two spermidine synthases; spermine synthase; flavin-dependent polyamine oxidases (SlPAO4-like and SlPAO2) and copper dependent amine oxidases (SlCuAO and SlCuAO-like). The spatiotemporal transcript abundances using qRT-PCR revealed presence of their transcripts in all tissues examined, with higher transcript levels observed for SAMDC1, SAMDC2 and ADC2 in most tissues. Cellular levels of free and conjugated forms of putrescine and spermidine were found to decline during heat stress while they increased in response to cold stress, revealing their differential responses. Transcript levels of ARG2, SPDS2, and PAO4-like increased in response to both heat and cold stresses. However, transcript levels of ARG1/2, AIH1, CPA, SPDS1 and CuAO4 increased in response to heat while those of ARG2, ADC1,2, ODC1, SAMDC1,2,3, PAO2 and CuPAO4-like increased in response to cold stress, respectively. Transcripts of ADC1,2, ODC1,2, and SPMS declined in response to heat stress while ODC2 transcripts declined under cold stress. These results show differential expression of PA metabolism genes under heat and cold stresses with more impairment clearly seen under heat stress. We interpret these results to indicate a more pronounced role of PAs in cold stress acclimation compared to that under heat stress in tomato leaves.

Transcript Abundance Patterns of 9- and 13-Lipoxygenase Subfamily Gene Members in Response to Abiotic Stresses (Heat, Cold, Drought or Salt) in Tomato (Solanum lycopersicum L.) Highlights Member-Specific Dynamics Relevant to Each Stress

Lipoxygenases (LOXs; EC 1.13.11.12) catalyze the oxygenation of fatty acids to produce oxylipins including the jasmonate family of plant hormones. The involvement of jasmonates in plant growth and development and during abiotic stress has been documented, however, the response and regulation of each member of the LOX gene family under various abiotic stresses is yet to be fully deciphered. Previously, we identified fourteen members of the tomato LOX gene family, which were divisible into nine genes representing the 9-LOX family members and five others representing the 13-LOX family members based on the carbon oxidation position specificity of polyunsaturated fatty acids. Here, we have determined the transcript abundance patterns of all the 14 LOX genes in response to four independent abiotic stresses, namely, heat, cold, drought and salt. Our results show that each of these stresses leads to a time-dependent, variable or indifferent response of specific and different set(s) of LOX gene members of both subfamilies, differentiating functional relevance of the 14 LOX genes analyzed. Out of the 14 gene members, three LOX genes were expressed constitutively or were non-responsive to either heat (SlLOX9), cold (SlLOX9) or salt (SlLOX4) stress. An in-silico LOX gene promoter search for stress-responsive elements revealed that only some but not all of the LOX genes indeed are decorated with specific and known stress responsive cis-acting elements. Thus, these data implicate some other, yet to be discovered, cis-acting elements present in the LOX gene family members, which seemingly regulate tomato responses to defined abiotic stresses presented here.

Polyamines: Bio-Molecules with Diverse Functions in Plant and Human Health and Disease

Biogenic amines-polyamines (PAs), particularly putrescine, spermidine and spermine are ubiquitous in all living cells. Their indispensable roles in many biochemical and physiological processes are becoming commonly known, including promoters of plant life and differential roles in human health and disease. PAs positively impact cellular functions in plants-exemplified by increasing longevity, reviving physiological memory, enhancing carbon and nitrogen resource allocation/signaling, as well as in plant development and responses to extreme environments. Thus, one or more PAs are commonly found in genomic and metabolomics studies using plants, particulary during different abiotic stresses. In humans, a general decline in PA levels with aging occurs parallel with some human health disorders. Also, high PA dose is detrimental to patients suffering from cancer, aging, innate immunity and cognitive impairment during Alzheimer and Parkinson diseases. A dichotomy exists in that while PAs may increase longevity and reduce some age-associated cardiovascular diseases, in disease conditions involving higher cellular proliferation, their intake has negative consequences. Thus, it is essential that PA levels be rigorously quantified in edible plant sources as well as in dietary meats. Such a database can be a guide for medical experts in order to recommend which foods/meats a patient may consume and which ones to avoid. Accordingly, designing both high and low polyamine diets for human consumption are in vogue, particularly in medical conditions where PA intake may be detrimental, for instance, cancer patients. In this review, literature data has been collated for the levels of the three main PAs, putrescine, spermidine and spermine, in different edible sources-vegetables, fruits, cereals, nuts, meat, sea food, cheese, milk, and eggs. Based on our analysis of vast literature, the effects of PAs in human/animal health fall into two broad, Yang and Yin, categories: beneficial for the physiological processes in healthy cells and detrimental under pathological conditions.

Fruit metabolite networks in engineered and non-engineered tomato genotypes reveal fluidity in a hormone and agroecosystem specific manner

INTRODUCTION

Metabolomics provides a view of endogenous metabolic patterns not only during plant growth, development and senescence but also in response to genetic events, environment and disease. The effects of the field environment on plant hormone-specific metabolite profiles are largely unknown. Few studies have analyzed useful phenotypes generated by introducing single or multiple gene events alongside the non-engineered wild type control at field scale to determine the robustness of the genetic trait and its modulation in the metabolome as a function of specific agroecosystem environments.

OBJECTIVES

We evaluated the influence of genetic background (high polyamine lines; low methyl jasmonate line; low ethylene line; and isogenic genotypes carrying double transgenic events) and environments (hairy vetch, rye, plastic black mulch and bare soil mulching systems) on the metabolomic profile of isogenic reverse genetic mutations and selected mulch based cropping systems in tomato fruit. Net photosynthesis and fruit yield were also determined.

METHODS

NMR spectroscopy was used for quantifying metabolites that are central to primary metabolism. We analyzed both the first moment (means) of metabolic response to genotypes and agroecosystems by traditional univariate/multivariate methods, and the second moment (covariances) of responses by creating networks that depicted changes in correlations of paired metabolites. This particular approach is novel and was necessary because our experimental material yielded highly variable metabolic responses that could not be easily understood using the traditional analytical approaches for first moment statistics.

RESULTS

High endogenous spermidine and spermine content exhibited strong effects on amino acids, Krebs cycle intermediates and energy molecules (ADP + ATP) in ripening fruits of plants grown under different agroecosystem environments. The metabolic response to high polyamine genotypes was similar to the response to hairy vetch cover crop mulch; supported by the pattern of changes in correlation between metabolites. Changes in primary metabolites of genotypes mutated for the deficiency of ethylene or methyl jasmonate were unique under all growth conditions and opposite of high polyamine genotype results. The high polyamine trait was found to dominate the low ethylene and low jasmonate mutations under field conditions. For several metabolites low ethylene and low methyl jasmonate genotypes had an inverse relationship. Collectively, these results affirm that interactions between metabolite pathways and growth environments are affected by genotype, and influence the metabolite quality of a crop.

CONCLUSION

This study portrays how metabolite relationships change, both in mean and in correlation, under different genotypic and environmental conditions. Although these networks are surprisingly dynamic, we also find examples of selectively conserved associations.