Aluminum or Low pH – Which Is the Bigger Enemy of Barley? Transcriptome Analysis of Barley Root Meristem Under Al and Low pH Stress

Aluminum (Al) toxicity is considered to be the most harmful abiotic stress in acidic soils that today comprise more than 50% of the world’s arable lands. Barley belongs to a group of crops that are most sensitive to Al in low pH soils. We present the RNA-seq analysis of root meristems of barley seedlings grown in hydroponics at optimal pH (6.0), low pH (4.0), and low pH with Al (10 μM of bioavailable Al3+ ions). Two independent experiments were conducted: with short-term (24 h) and long-term (7 days) Al treatment. In the short-term experiment, more genes were differentially expressed (DEGs) between root meristems grown at pH = 6.0 and pH = 4.0, than between those grown at pH = 4.0 with and without Al treatment. The genes upregulated by low pH were associated mainly with response to oxidative stress, cell wall organization, and iron ion binding. Among genes upregulated by Al, overrepresented were those related to response to stress condition and calcium ion binding. In the long-term experiment, the number of DEGs between hydroponics at pH = 4.0 and 6.0 were lower than in the short-term experiment, which suggests that plants partially adapted to the low pH. Interestingly, 7 days Al treatment caused massive changes in the transcriptome profile. Over 4,000 genes were upregulated and almost 2,000 genes were downregulated by long-term Al stress. These DEGs were related to stress response, cell wall development and metal ion transport. Based on our results we can assume that both, Al3+ ions and low pH are harmful to barley plants. Additionally, we phenotyped the root system of barley seedlings grown in the same hydroponic conditions for 7 days at pH = 6.0, pH = 4.0, and pH = 4.0 with Al. The results correspond to transcriptomic data and show that low pH itself is a stress factor that causes a significant reduction of root growth and the addition of aluminum further increases this reduction. It should be noted that in acidic arable lands, plants are exposed simultaneously to both of these stresses. The presented transcriptome analysis may help to find potential targets for breeding barley plants that are more tolerant to such conditions.

Membrane-Enriched Proteomics Link Ribosome Accumulation and Proteome Reprogramming With Cold Acclimation in Barley Root Meristems

Due to their sessile nature, plants rely on root systems to mediate many biotic and abiotic cues. To overcome these challenges, the root proteome is shaped to specific responses. Proteome-wide reprogramming events are magnified in meristems due to their active protein production. Using meristems as a test system, here, we study the major rewiring that plants undergo during cold acclimation. We performed tandem mass tag-based bottom-up quantitative proteomics of two consecutive segments of barley seminal root apexes subjected to suboptimal temperatures. After comparing changes in total and ribosomal protein (RP) fraction-enriched contents with shifts in individual protein abundances, we report ribosome accumulation accompanied by an intricate translational reprogramming in the distal apex zone. Reprogramming ranges from increases in ribosome biogenesis to protein folding factors and suggests roles for cold-specific RP paralogs. Ribosome biogenesis is the largest cellular investment; thus, the vast accumulation of ribosomes and specific translation-related proteins during cold acclimation could imply a divergent ribosomal population that would lead to a proteome shift across the root. Consequently, beyond the translational reprogramming, we report a proteome rewiring. First, triggered protein accumulation includes spliceosome activity in the root tip and a ubiquitous upregulation of glutathione production and S-glutathionylation (S-GSH) assemblage machineries in both root zones. Second, triggered protein depletion includes intrinsically enriched proteins in the tip-adjacent zone, which comprise the plant immune system. In summary, ribosome and translation-related protein accumulation happens concomitantly to a proteome reprogramming in barley root meristems during cold acclimation. The cold-accumulated proteome is functionally implicated in feedbacking transcript to protein translation at both ends and could guide cold acclimation.

The cell fate controlling CLE40 peptide requires CNGC9 to trigger highly localized Ca2+ transients in Arabidopsis thaliana root meristems

Communication between plant cells and their biotic environment is largely dependent on the function of plasma membrane localized receptor-like kinases (RLKs). Major players in this communication within root meristems are secreted peptides, including CLAVATA3/EMBRYO SURROUNDING REGION40 (CLE40). In the distal root meristem, CLE40 acts through the receptor like kinase (RLK) ARABIDOPSIS CRINKLY4 (ACR4) and the leucine-rich repeat (LRR) RLK CLAVATA1 (CLV1) to promote cell differentiation. In the proximal meristem, CLE40 signalling requires the LRR receptor-like protein (RLP) CLAVATA2 (CLV2) and the membrane localized pseudokinase CORYNE (CRN), and serves to inhibit cell differentiation. The molecular components that act immediately downstream of the CLE40-activated receptors are not yet known. Here we show that active CLE40 signalling triggers the release of intracellular Ca2+ leading to increased cytosolic Ca2+ concentration ([Ca2+]cyt) in a subset of proximal root meristem cells. This rise in [Ca2+]cyt depends on the CYCLIC NUCLEOTIDE GATED CHANNEL 9 (CNGC9), CLV1, the CLV1-related BARELY ANY MERISTEM1 (BAM1), CLV2 and CRN. The precise function of changes in [Ca2+]cyt are not yet known, but might form a central part of a fine-tuned response to CLE40 peptide that serves to integrate root meristem growth with stem cell fate decisions and initiation of lateral root primordia.

The effect of red light (660 nm) on proliferative activity and growth reactions in seedlings of plants with contrast photoperiodic reaction

The results of a study of the effect of red light irradiation (660 nm) on the proliferative activity of root meristems and growth reactions of plant seedlings with contrast photoperiodic reactions are presented in this paper. Plants of the family Fabaceae contrasting in the photoperiodic reaction were used as plant material: long-day plants (LDP) of peas (Pisum sativum L.) of the Metsenat variety and short-day plants (SDP) of soybean (Glycine max (L.) Merr.) of the Korsak variety. Phytochromes were activated by irradiating the aerial part of the experimental seedlings with monochromatic red light (RL) of 660 nm using an LED matrix for 30 minutes for 5 days. The proliferative activity of meristem cells was determined by analysis of the mitotic index (MI). The growth reaction was studied by linear growth indicators: the total length of the seedling, the length of the aerial part and roots, and the integral indicator of growth and biosynthetic processes – the accumulation of biomass. According to the results of the experiments, it was shown that the mitotic activity of root meristems under the influence of red light on the aerial part in seedlings of the LDP of pea Metsenat decreased slightly – by 8 %, and in the seedlings of the SDP of soybean Korsak increased significantly – by 47 %. The linear growth and accumulation of biomass in the aerial part under the action of RL irradiation in seedlings of pea of the Metsenat variety and soybean of the Korsak variety decreased, and this effect was more pronounced in soybean than in pea. During irradiation of RL the linear root growth and their biomass accumulation in seedlings of LDP pea decreased slightly, while at the same time, these processes in the roots of soybean SDP seedlings were significantly stimulated. Under the influence of RL in pea seedlings, the growth rate did not change in the length of the aerial part, but in the roots increased, while the rate of biomass accumulation by them decreased. In soybean seedlings during RL irradiation, the growth rate of both the aerial part and the roots decreased, the biomass accumulation rate by the aerial part increased, and by the roots – decreased. LDP of pea Metsenat and SDP of soybean Korsak variety differ in the nature of the reaction of growth processes in response to irradiation of RL. The activation of the phytochrome system in the aerial part causes changes in the proliferative activity and growth processes of the roots, which indicate a systemic response of the plant organism to the action of this factor. The relationship of the photoperiodic reaction of plants with the realization of phytochrome signal in the plant by activating or inhibiting the proliferative activity of root meristems and growth reactions is discussed.

Control of gamete origin of white cabbage regenerants in anther culture in vitro

The complex use of indirect methods (counting chloroplasts in stomatal cells, as well as direct counting of chromosomes in preparations of root meristems) in combination with DNA methods makes it possible to identify ploidy of plants obtained from white cabbage anthers and to rank them on haploids / doubled haploids and diploid ones already on test tube level.