Jeevan R. Singiri

Early and recent studies have demonstrated that exposure to moonlight influences the entire life cycle of plants from seed germination to vegetative growth and reproduction. Exposure to moonlight was found to induce genome reorganization in plants and significant changes in gene expression, protein, and metabolite profiles. However, the specific factors that facilitate moonlight perception are unknown. To uncover the photoreceptors responsible for moonlight perception, we analyzed Arabidopsis phototropin mutants (phot1, phot2, and phot1phot2) as well as the phytochrome mutants phyA and phyB for their response to full moonlight (FML). De-etiolation assays revealed that plants do perceive and respond to FML within 5 h of exposure. Thus, among the photoreceptor mutants analyzed, only phot1 and phot1phot2 were impaired in apical hook opening and cotyledon unfolding under FML. Interestingly, under high light intensity, all examined mutants underwent proper de-etiolation. Further analysis showed that phot1 as well as phyB mutants were impaired in response to moonlight, displaying no changes in nuclear size and in protein profiles following exposure to FML and were comparable to plants exposed to dark. The FML (5 h exposure) did not induce the formation of fewer, large nuclear photobodies, as occurred following 5 h exposure to growth-room light. Our findings highlighted phot1 and phyB as photoreceptors necessary for plants to perceive and respond to FML. It is proposed that the initial perception of moonlight is facilitated by the blue-light receptor phot1 and is subsequently interpreted into a functional state by the R/FR receptor phyB.

Early and recent studies have demonstrated that exposure to moonlight influences the entire life cycle of plants from seed germination to vegetative growth and reproduction. Exposure to moonlight was found to induce genome reorganization in plants and significant changes in gene expression, protein, and metabolite profiles. However, the specific factors that facilitate moonlight perception are unknown. To uncover the photoreceptors responsible for moonlight perception, we analyzed Arabidopsis phototropin mutants (phot1, phot2, and phot1phot2) as well as the phytochrome mutants phyA and phyB for their response to full moonlight (FML). De-etiolation assays revealed that plants do perceive and respond to FML within 5 h of exposure. Thus, among the photoreceptor mutants analyzed, only phot1 and phot1phot2 were impaired in apical hook opening and cotyledon unfolding under FML. Interestingly, under high light intensity, all examined mutants have undergone proper de-etiolation. Further analysis showed that phot1 as well as phyB mutants were impaired in response to moonlight, displaying no changes in nuclear size and in protein profiles following exposure to FML and were comparable to plants exposed to dark. The FML (5 h exposure) did not induce the formation of fewer, large nuclear photobodies as occurred following 5 h exposure to growth room light. Our findings highlighted phot1 and phyB as photoreceptors necessary for plants to perceive and respond to FML. It is proposed that the initial perception of moonlight is facilitated by the blue light receptor phot1 and is subsequently interpreted into a functional state by the R/FR receptor phyB.

Rhythmic exposure to moonlight has been shown to affect animal behavior, but its effects on plants, often observed in lunar agriculture, have been doubted and often regarded as myth. Consequently, lunar farming practices are not well scientifically supported, and the influence of this conspicuous environmental factor, the moon, on plant cell biology has hardly been investigated. We studied the effect of full moonlight (FML) on plant cell biology and examined changes in genome organization, protein and primary metabolite profiles in tobacco and mustard plants and the effect of FML on the post-germination growth of mustard seedlings. Exposure to FML was accompanied by a significant increase in nuclear size, changes in DNA methylation and cleavage of the histone H3 C-terminal region. Primary metabolites associated with stress were significantly increased along with the expression of stress-associated proteins and the photoreceptors phytochrome B and phototropin 2; new moon experiments disproved the light pollution effect. Exposure of mustard seedlings to FML enhanced growth. Thus, our data show that despite the low-intensity light emitted by the moon, it is an important environmental factor perceived by plants as a signal, leading to alteration in cellular activities and enhancement of plant growth.

Plants have two types of reproduction: sexual, resulting in embryo production, and asexual, resulting in vegetative bodies commonly derived from stems and roots (e.g., bulb, tuber). Dead organs enclosing embryos (DOEEs, such as seed coat and pericarp) are emerging as central components of the dispersal unit acting to nurture the embryo and ensure its survival in the habitat. Here we wanted to investigate the properties of dead organs enclosing plant asexual reproductive bodies, focusing on the garlic (Allium sativum) bulb. We investigated the biochemical and biological properties of the outer peel enclosing the bulb and the inner peel enclosing the clove using various methodologies, including bioassays, proteomics, and metabolomics. The garlic peels differentially affected germination and post-germination growth, with the outer peel demonstrating a strong negative effect on seed germination of Sinapis alba and on post-germination growth of Brassica juncea. Proteome analysis showed that dead garlic peels possess 67 proteins, including chitinases and proteases, which retained their enzymatic activity. Among primary metabolites identified in garlic peels, the outer peel accumulated multiple sugars, including rhamnose, mannitol, sorbitol, and trehalose, as well as the modified amino acid 5-hydroxylysine, known as a major component of collagen, at a higher level compared to the clove and the inner peel. Growth of Escherichia coli and Staphylococcus aureus was promoted by garlic peel extracts but inhibited by clove extract. All extracts strongly inhibited spore germination of Fusarium oxysporum f.sp. melonis. Thus, the garlic peels not only provide physical protection to vegetative offspring but also appear to function as a refined arsenal of proteins and metabolites for enhancing growth and development, combating potential pathogens, and conferring tolerance to abiotic stresses.

The seed is the fundamental unit of the dispersal of dry, dehiscent fruits, in which the fruit splits open at maturity to allow for seed dispersal. However, dry fruits may be indehiscent and therefore represent the dispersal unit (DU). Cereals possess a one-seeded fruit, whereby the seed coat and the fruit coat are fused together to generate the caryopsis. This caryopsis may be covered by floral bracts to generate two types of DUs, namely florets, whereby the caryopsis is enclosed by the lemma and the palea (e.g., Avenasterilis) or spikelet, whereby the floret(s) is further covered by the glumes (Triticum turgidum var. dicoccoides). Here, we highlight the dead coverings enclosing the caryopsis in cereals, namely the husks as an integral component of the dispersal unit that play multifaceted roles in grain biology. Thus, besides protection and dispersal means, the husks function as a rich maternal supply of proteins and metabolites for enhancing growth and development, combat potential pathogens as well as confer tolerance to abiotic stresses. These attributes might have broad implications for crop performance, plant population dynamics and diversity in ecological systems, and for conservation of genetic resources in seed banks.

In the face of climate change and the predicted increase in the frequency and severity of abiotic stresses (e.g., hot spell, salinity), we sought to investigate the effect of salinity (S), short episodes of high temperature (HS) and combination of salinity and high temperature (SHS), at the reproductive phase, on yield with a special focus on the properties of dead pericarps of Brassica juncea. Three interval exposures to HS resulted in massive seed abortion, and seeds from salt-treated plants germinated poorly. Germination rate and final germination of B. juncea seeds were slightly reduced in the presence of salt and SHS pericarp extracts. All pericarp extracts completely inhibited seed germination of tomato and Arabidopsis, but removal of pericarp extracts almost fully restored seed germination. Heat and salinity profoundly affected the accumulation of phytohormones in dead pericarps. Combined stresses highly reduced IAA and ABA levels compared with salt, and enhanced the accumulation of GA1, but abolished the positive effect of salt on the accumulation of GA4, JA and SA. Interestingly, pericarp extracts displayed priming activity and significantly affected seedling performance in a manner dependent on the species and on the origin of the pericarp. While control pericarps improved and reduced the seedlings’ performance of autologous and heterologous species, respectively, pericarps from salt-treated plants were harmless or improved heterologous seedling performance. Thus, the strategy employed by the germinating seed for securing resources is set up, at least partly, by the mother plant in conjunction with the maternal environment whose components are stored in the dead maternal organs enclosing the embryo.

Dead organs enclosing embryos, such as seed coats and pericarps, are emerging as important maternally-derived components of the dispersal unit that affect seed performance and fate. In the face of climate change and increased incidents of heatwaves, we sought to investigate the effect of salinity (S), short episodes of high temperature (HS), and combination of S + HS (SHS), at the reproductive phase, on the properties of dead pericarps of Brassica juncea. Proteome and metabolome analyses revealed multiple proteins and metabolites stored in dead pericarps whose levels and composition were altered under single and combined stress conditions. The protein profile of SHS showed a higher correlation with salt than with HS indicating the dominant effect of salt over heat stress. On the other hand, the analysis of metabolites showed that the profile of SHS has better correlation with HS than with salt. The integration of metabolic and proteomic data showed that changes in TCA cycle intermediates and certain amino acids (e.g., proline) under salt treatments (S and SHS) are highly correlated with changes in proteins involved in their biosynthetic pathways. Thus, accumulation of proteins and metabolites in dead pericarps is differently affected by single and combination of salt and heat stresses. Salinity appears to dominate plant response to combined stresses at the protein level, while heat appears to be the major factor affecting metabolite accumulation in dead pericarps.