Research Progress on Plant Shaker K+ Channels

Plant growth and development are driven by intricate processes, with the cell membrane serving as a crucial interface between cells and their external environment. Maintaining balance and signal transduction across the cell membrane is essential for cellular stability and a host of life processes. Ion channels play a critical role in regulating intracellular ion concentrations and potentials. Among these, K+ channels on plant cell membranes are of paramount importance. The research of Shaker K+ channels has become a paradigm in the study of plant ion channels. This study offers a comprehensive overview of advancements in Shaker K+ channels, including insights into protein structure, function, regulatory mechanisms, and research techniques. Investigating Shaker K+ channels has enhanced our understanding of the regulatory mechanisms governing ion absorption and transport in plant cells. This knowledge offers invaluable guidance for enhancing crop yields and improving resistance to environmental stressors. Moreover, an extensive review of research methodologies in Shaker K+ channel studies provides essential reference solutions for researchers, promoting further advancements in ion channel research.

Genome-wide identification of Shaker K+ channel family in Nicotiana tabacum and functional analysis of NtSKOR1B in response to salt stress

Soil salinization poses a mounting global ecological and environmental threat. The identification of genes responsible for negative regulation of salt tolerance and their utilization in crop improvement through gene editing technologies emerges as a swift strategy for the effective utilization of saline-alkali lands. One efficient mechanism of plant salt tolerance is maintaining the proper intracellular K+/Na+ ratio. The Shaker K+ channels play a crucial role in potassium absorption, transport, and intracellular potassium homeostasis in plant cells. Here, the study presents the first genome-wide identification of Shaker K+ channels in Nicotiana tabacum L., along with a detailed bioinformatic analysis of the 20 identified members. Transcriptome analysis revealed a significant up-regulation of NtSKOR1B, an outwardly-rectifying member predominantly expressed in the root tissue of tobacco seedlings, in response to salt stress. This finding was then confirmed by GUS staining of ProNtSKOR1B::GUS transgenic lines and RT-qPCR analysis. Subsequently, NtSKOR1B knockout mutants (ntskor1) were then generated and subjected to salt conditions. It was found that ntskor1 mutants exhibit enhanced salt tolerance, characterized by increased biomass, higher K+ content and elevated K+/Na+ ratios in both leaf and root tissues, compared to wild-type plants. These results indicate that NtSKOR1B knockout inhibits K+ efflux in root and leaf tissues of tobacco seedlings under salt stress, thereby maintaining higher K+/Na+ ratios within the cells. Thus, our study identifies NtSKOR1B as a negative regulator of salt tolerance in tobacco seedlings.

The Roles of Calcineurin B-like Proteins in Plants under Salt Stress

Salinity stands as a significant environmental stressor, severely impacting crop productivity. Plants exposed to salt stress undergo physiological alterations that influence their growth and development. Meanwhile, plants have also evolved mechanisms to endure the detrimental effects of salinity-induced salt stress. Within plants, Calcineurin B-like (CBL) proteins act as vital Ca2+ sensors, binding to Ca2+ and subsequently transmitting signals to downstream response pathways. CBLs engage with CBL-interacting protein kinases (CIPKs), forming complexes that regulate a multitude of plant growth and developmental processes, notably ion homeostasis in response to salinity conditions. This review introduces the repercussions of salt stress, including osmotic stress, diminished photosynthesis, and oxidative damage. It also explores how CBLs modulate the response to salt stress in plants, outlining the functions of the CBL-CIPK modules involved. Comprehending the mechanisms through which CBL proteins mediate salt tolerance can accelerate the development of cultivars resistant to salinity.

Determination of optimal NH4+/K + concentration and corresponding ratio critical for growth of tobacco seedlings in a hydroponic system

Inherently, ammonium (NH₄ ⁺) is critical for plant growth; however, its toxicity suppresses potassium (K⁺) uptake and vice-versa. Hence, attaining a nutritional balance between these two ions (NH₄ ⁺ and K⁺) becomes imperative for the growth of tobacco seedlings. Therefore, we conducted a 15-day experimental study on tobacco seedlings exposed to different concentrations (47 treatments) of NH₄ ⁺/K⁺ at different corresponding 12 ratios simultaneously in a hydroponic system. Our study aimed at establishing the optimal NH₄ ⁺-K⁺ concentration and the corresponding ratio required for optimal growth of different tobacco plant organs during the seedling stage. The controls were the baseline for comparison in this study. Plants with low or excessive NH₄ ⁺-K⁺ concentration had leaf chlorosis or dark greenish colouration, stunted whole plant part biomass, and thin roots. We found that adequate K⁺ supply is a pragmatic way to mitigate NH₄ ⁺-induced toxicity in tobacco plants. The optimal growth for tobacco leaf and root was attained at NH₄ ⁺-K⁺ concentrations 2-2 mM (ratio 1:1), whereas stem growth was optimal at NH₄ ⁺-K⁺ 1-2 mM (1:2). The study provided an insight into the right combination of NH₄ ⁺/K⁺ that could mitigate or prevent NH₄ ⁺ or K⁺ stress in the tobacco seedlings.

Differential Effects of Ammonium (NH4+) and Potassium (K+) Nutrition on Photoassimilate Partitioning and Growth of Tobacco Seedlings

Plants utilize carbohydrates as the main energy source, but much focus has been on the impact of N and K on plant growth. Less is known about the combined impact of NH₄⁺ and K⁺ nutrition on photoassimilate distribution among plant organs, and the resultant effect of such distribution on growth of tobacco seedlings, hence this study. Here, we investigated the synergetic effect of NH₄⁺ and K⁺ nutrition on photoassimilate distribution, and their resultant effect on growth of tobacco seedlings. Soluble sugar and starch content peaks under moderate NH₄⁺ and moderate K⁺ (2-2 mM), leading to improved plant growth, as evidenced by the increase in tobacco weight and root activity. Whereas, a drastic reduction in the above indicators was observed in plants under high NH₄⁺ and low K⁺ (20-0.2 mM), due to low carbohydrate synthesis and poor photoassimilate distribution. A strong positive linear relationship also exists between carbohydrate (soluble sugar and starch) and the activities of these enzymes but not for invertase. Our findings demonstrated that NH₄⁺ and K⁺-induced ion imbalance influences plant growth and is critical for photoassimilate distribution among organs of tobacco seedlings.

KIR genotyping by reverse sequence-specific oligonucleotide methodology

Recent studies suggest that killer cell immunoglobulin-like receptors (KIR) genotyping may be relevant to bone marrow/stem cell transplantation. The objective of this research was to develop a bead-based reverse sequence-specific oligonucleotide DNA hybridization assay for KIR genotyping using the Luminex platform. The oligonucleotide probes were designed to recognize 14 currently known KIR genes and two pseudogenes, as well as null alleles. A unique probe design was used to allow detection of two cis-polymorphic regions for typing of KIR2DS4, because the functioning alleles cannot readily be assigned by conventional probe detection systems. Assay performance was validated using DNA samples previously typed by the 13th International Histocompatibility Working Group with 100% concordant results.

Color Doppler imaging in the study of retrobulbar hemodynamic changes of primary angle-closure glaucoma

PURPOSE

To investigate the hemodynamic changes of ophthalmic and central retinal artery (OA, CRA) in Primary Angle-closure Glaucoma (PACG) and the effects of intraocular pressure (IOP) on the retrobulbar hemodynamics.

METHODS

The hemodynamic changes of OA, CRA in PACG were explored with color Doppler imaging (CDI) technique. Peak systolic blood flow velocity (PSV), end-diastolic blood flow velocity (EDV), pulsatile and resistive indices (PI, RI) were recorded and compared with those of the normal subjects. There were 20 patients (40 eyes) with PACG who were divided into two groups according to their IOP levels: ocular hypertension (15 eyes) and normal tension (25 eyes).

RESULTS

Compared with the normal subjects, the hypertension group of PACG showed significant reduction in the EDV and increases in PI, RI of CRA; normal tension group of PACG also showed remarkable increase in RI of CRA. The ocular hypertension was significantly correlated with the RI and not with the EDV by the analysis of multiple linear regression (the partial correlation coefficient for IOP vs RI was 0.388, p = 0.0234, for IOP vs EDV was 0.053, p = 0.7688). Compared with the normal group, there might be a trend of reduction in the EDV of the OA in PACG group.

CONCLUSION

Intraocular pressure elevated is a major cause of the vascular resistance increased in PACG, which will make the end-diastolic blood flow of CRA decreased. There exists an abnormal vascular resistance in the normal tension eyes of PACG.