Stomatal Opening Research Articles

Carbon gain is coordinated with enhanced stomatal conductance and hydraulic architecture in coffee plants acclimated to elevated [CO2]: The interplay with irradiance supply

We recently demonstrated that, under elevated [CO2] (eCa), coffee (Coffea arabica L.) plants grown at high light (HL), but not at low light (LL), display higher stomatal conductance (gs) than at ambient [CO2] (aCa). We then hypothesized that the enhanced gs at eCa/HL, if sustained at the long-term, would lead to adjustments in hydraulic architecture. To test this hypothesis, potted plants of coffee were grown in open-top chambers for 12 months under HL or LL (ca. 9 or 1 mol photons m−2 day−1, respectively); these light treatments were combined with two [CO2] levels (ca. 437 or 705 μmol mol−1, respectively). Under eCa/HL, increased gs was closely accompanied by increases in branch and leaf hydraulic conductances, suggesting a coordinated response between liquid- and vapor-phase water flows throughout the plant. Still under HL, eCa also resulted in increased Huber value (sapwood area-to-total leaf area), sapwood area-to-stem diameter, and root mass-to-total leaf area, thus further improving the water supply to the leaves. Our results demonstrate that Ca is a central player in coffee physiology increasing carbon gain through a close association between stomatal function and an improved hydraulic architecture under HL conditions.

APLIKASI PUPUK KALIUM CAIR PLUS UNTUK MENINGKATKAN KUALITAS BAWANG MERAH DI ADIPALA, CILACAP

One of the important factors influencing crop production is nutrition, which depends on soil fertility and fertilizer application. Nutrition will affect the weight loss of shallots. Shallots can loss weight loss of 25-40% during drying and 17% during storage. One of the nutrients that affect weight loss is potassium. Potassium is an element that plays an important role for plants in the process of photosynthesis, energy storage, protein synthesis, translocation of photosynthetic products. Potassium also plays a role in protecting the osmotic potential of plants in regulating the closing and opening of stomata so that plants can maintain water conditions which will have a good impact on photosynthesis and the flow of assimilate from leaves to plant parts. This study aimed to determine the effect of liquid potassium fertilizer plus application on the quality of shallots. The research was conducted in Adipala, Cilacap which has a height of 10 m above sea level and a temperature ranging from 23-30o C. The land area used is 50 m2. The study was conducted from June 2021 to September 2021. This study used a non-factorial randomized block design with four treatments, namely (1) 0 ml/plot, (2) 1 ml/plot, (3) 1.5 ml/plot, and (4) 2 ml/plot with ten replications. Data were analised using Anova and than follow DMRT at error 0,5%. The variables observed were: plant height, number of leaves, number of bulb, total fresh weight, total dry weight of askip, bulb diameter, bulb hardness and crop yield/plot. The results showed that the application of liquid potassium fertilizer plus had no significant effect on plant height, number of leaves, number of bulb, total fresh weight, total dry weight of askip, blub diameter, and crop yield/plot, but significantly affected the hardness of shallot bulbs.

Diurnal decline in photosynthesis and stomatal conductance in several tropical species.

Photosynthesis (A) and stomatal conductance (gs) change diurnally due to internal signals, but the effects of diurnal rhythms on dynamic photosynthetic behavior are understudied. We examined diurnal changes in A and gs in ten tropical species: across species, there was a tendency for A and gs to decline diurnally when these were repeatedly measured under either steady-state or fluctuating irradiance conditions. We then examined in more detail the irradiance-induced kinetics of gas exchange in a C3 and C4 crop species each, namely fig (Ficus carica) and sugarcane (Saccharum officinarum). During the day, fig showed significantly slower photosynthetic induction and lower gs, as well as a slower gs increase, in the afternoon than in the morning and noon. Sugarcane showed a reduction in steady-state A reached under high irradiance and slower gs increase as well as lower gs reached under high irradiance, but no changes in the rate of photosynthetic induction, in the afternoon, compared to morning and noon. These reductions in the afternoon were not reverted by a dark treatment in the middle of the day, suggesting that the decrease was not proportional to diurnal time-integrated carbon fixation. Repeated exposure to light- and shadeflecks (1000 and 50 μmol m-2 s-1, lasting 20 min each) revealed fundamental differences in stomatal regulation between species: in fig, stomata opened and closed slowly, and their opening became progressively slower under a series of lightflecks, whereas sugarcane showed much faster stomatal opening than closure that was unchanged during the course of the day. Our results highlight that steady-state rates and irradiance-induced kinetics of photosynthesis and stomatal movement change diurnally in most species studied, and that they do so differently in fig and sugarcane.

Phytohormonal modulation of the drought stress in soybean: outlook, research progress, and cross-talk.

Phytohormones play vital roles in stress modulation and enhancing the growth of plants. They interact with one another to produce programmed signaling responses by regulating gene expression. Environmental stress, including drought stress, hampers food and energy security. Drought is abiotic stress that negatively affects the productivity of the crops. Abscisic acid (ABA) acts as a prime controller during an acute transient response that leads to stomatal closure. Under long-term stress conditions, ABA interacts with other hormones, such as jasmonic acid (JA), gibberellins (GAs), salicylic acid (SA), and brassinosteroids (BRs), to promote stomatal closure by regulating genetic expression. Regarding antagonistic approaches, cytokinins (CK) and auxins (IAA) regulate stomatal opening. Exogenous application of phytohormone enhances drought stress tolerance in soybean. Thus, phytohormone-producing microbes have received considerable attention from researchers owing to their ability to enhance drought-stress tolerance and regulate biological processes in plants. The present study was conducted to summarize the role of phytohormones (exogenous and endogenous) and their corresponding microbes in drought stress tolerance in model plant soybean. A total of n=137 relevant studies were collected and reviewed using different research databases.

Maternal Embryo Effect Arrest 31 (MEE31) is a moonlighting protein involved in GDP-D-mannose biosynthesis and KAT1 potassium channel regulation

Due to anthropogenic global warming, droughts are expected to increase and water availability to decrease in the coming decades. For this reason, research is increasingly focused on developing plant varieties and crop cultivars with reduced water consumption. Transpiration occurs through stomatal pores, resulting in water loss. Potassium plays a significant role in stomatal regulation. KAT1 is an inward-rectifying potassium channel that contributes to stomatal opening. Using a yeast high-throughput screening of an Arabidopsis cDNA library, MEE31 was found to physically interact with KAT1. MEE31 was initially identified in a screen for mutants with delayed embryonic development. The gene encodes a conserved phosphomannose isomerase (PMI). We report here that MEE31 interacts with and increases KAT1 activity in yeast and this interaction was also confirmed in plants. In addition, MEE31 complements the function of the yeast homologue, whereas the truncated version recovered in the screening does not, thus uncoupling the enzymatic activity from KAT1 regulation. We show that MEE31 overexpression leads to increased stomatal opening in Arabidopsis transgenic lines. Our data suggest that MEE31 is a moonlighting protein involved in both GDP-D-mannose biosynthesis and KAT1 regulation.

Increasing mustard (Brassica juncea L.) yields through exposure sound and preventive pest management based on refugia plants

Abstract. In Indonesia, mustard plants will increase by 8.2% in 2021, but more than that is needed to meet the community's needs due to a growing population. Pests and fertilization problems hinder expected growth. The provision of plant fertilizers can be replaced through the application of sound. Exposure sounds to plants can increase plant growth by opening stomata, improving water absorption, and increasing plant nutrient uptake. This study aimed to examine the application of sound effects and refugia plants t890po increase the growth and yield of mustard greens (Brassica juncea L.). The study used a Time's Series Randomized Block Design with 3 replications. The first factor is sound applications (S) consisting of S0 = without sound, S1 = rock music (Frequency 21-14,000 Hz), and S2 = classical sound (Frequency 21-14,000 Hz). The second factor is the refugia plant (R) consisting of R0 = without refugia, R1 = Tagetes erecta L., R2 = Zinnia elegans L, and R3 = Ocimum bassilicum L. The application of classical sound frequency (20-14,000 Hz) affects the growth process of mustard plants through the increase in plant height (14.5%), leaf area (20.92%), wet weight (3.5%), dry weight (26.41%), total chlorophyll (11.62%) and plant N content (31.03%). Meanwhile, rock music frequency (20-14,000 Hz) can increase plant height (2.97%), leaf area (19.11%), and total stomata (9.6%). Refugia plants affect the process of plant protection through their ability to attract pests in the research area.

Does MPK4/12-HT1 function as a CO2/bicarbonate sensor to regulate the stomatal conductance under high CO2 levels?

Recently, a HT1 protein has been identified which causes continuous opening of stomata because of its kinase activity.However, reversible interaction between MAP4/12 and HT1 protein acts as a CO2/bicarbonate sensor and causes the closing of stomata by inhibiting HT1 kinase activity.

Perfluoroalkyl substances exposure alters stomatal opening and xylem hydraulics in willow plants

Climate change and pollution are increasingly important stress factors for life on Earth. Dispersal of poly- and perfluoroalkyl substances (PFAS) are causing worldwide contamination of soils and water tables. PFAS are partially hydrophobic and can easily bioaccumulate in living organisms, causing metabolic alterations. Different plant species can uptake large amounts of PFAS, but little is known about its consequences for the plant water relation and other physiological processes, especially in woody plants. In this study, we investigated the fractionation of PFAS bioaccumulation from roots to leaves and its effects on the conductive elements of willow plants. Additionally, we focused on the stomal opening and the phytohormonal content. For this purpose, willow cuttings were exposed to a mixture of 11 PFAS compounds and the uptake was evaluated by LC-MS/MS. Stomatal conductance was measured and the xylem vulnerability to air embolism was tested and further, the abscisic acid and salicylic acid contents were quantified using LC-MS/MS. PFAS accumulated from roots to leaves based on their chemical structure. PFAS-exposed plants showed reduced stomatal conductance, while no differences were observed in abscisic acid and salicylic acid contents. Interestingly, PFAS exposure caused a higher vulnerability to drought-induced xylem embolism in treated plants. Our study provides novel information about the PFAS effects on the xylem hydraulics, suggesting that the plant water balance may be affected by PFAS exposure. In this perspective, drought events may be more stressful for PFAS-exposed plants, thus reducing their potential for phytoremediation.

Metabolomic Analysis of Arabidopsis ost1-4 Mutant Revealed the Cold Response Regulation Mechanisms by OPEN STOMATA 1 (OST1) at Metabolic Level

Cold stress is one of the major abiotic stresses that limits the growth and development of plants. Improving the cold tolerance of plants is essential to enhance crop productivity in the changing environment. OPEN STOMATA 1 (OST1), also known as sucrose non-fermenting 1 related protein kinases 2.6/2E (SnRK2.6/SnRK2E), has been reported to involved in cold stress response in plants. This interesting protein is confined to expressed in guard cells and vascular system. However, the detailed mechanism of how OST1 regulates cold stress, especially at the metabolomic level is largely unknown. In this study, metabolomic profiling of ost1 mutant and WT Arabidopsis plants under cold stress was investigated. The results showed that ost1-4 mutants displayed cold sensitive phenotypes compared with the WT plant, as evidenced by higher MDA content and electrolyte leakage and lower photosynthetic characteristics. Next, the metabolic changes between ost1-4 and WT plants in response to cold stress was analyzed by using the GC-TOF-MS system. The results showed that numbers of metabolites were identified to be related to OST1 regulated cold stress response. A large portion of the metabolites were carbohydrates and organic acids. The KEGG enrichment analysis revealed that the alanine, aspartate and glutamate metabolism, cyanoamino acid metabolism and citrate cycle (TCA cycle) were presumptive pathways that most related to OST1 regulated cold stress response. Gene expression such as AtGDHs, AtPPC1 and AtAK1 was also in line with the metabolic changes in the presumed pathways. Overall, this study provides fundamental knowledge for understanding the underlying metabolic mechanisms of OST1 mediated cold stress response in plants.

Tolerance of <i>Capsicum frutescens</i> L. (Solanales: Solanaceae) to the duration of waterlogging and impact on the post-waterlogging and recovery periods

Waterlogging is a shallow flooding in the area of the root and in some parts of the shoot. It is one of the most common types of flooding in agricultural areas. The duration of waterlogging affects plant growth and yield in response to stress by interacting with their ability to adapt. Plant adaptability during waterlogging affects their resilience to post-waterlogging and recovery conditions. In this research, we examined the tolerance of Capsicum frutescens to short (1 day), medium (3 days) and long (10 days) duration of waterlogging, as well as its implications on post-waterlogging, recovery, reproductive phase and harvest. Adaptability and growth rates were used to determine plant tolerance to waterlogging stress. The percentage of wilting, root damage, survival, stomatal response, formation of hypertrophic lenticels, adventitious roots, photosynthetic pigment content, height, leaf number, plant biomass, flower number, and fruit fresh weight were used to measure adaptability and growth. The results showed that a longer duration of waterlogging increased root damage and decreased plant growth, affecting photosynthetic pigment content, leaf number, root and shoot biomass. The ability to regulate the stomata opening, the formation of hypertrophic lenticels and adventitious roots enabled plants not to wilt permanently, surviving post-waterlogging conditions and during recovery, growing during reproductive phase and producing yields. The critical duration of waterlogging at the beginning of the vegetative phase occurred at 10 days, and pepper suffered a drastic reduction in vegetative and reproductive growth and yields. The maintenance of the root system and the development of adaptive mechanisms increased plant survival, thereby affecting yield.

Update on stomata development and action under abiotic stress.

Stomata, key gatekeepers of plant hydration, have long been known to play a pivotal role in mitigating the impacts of abiotic stressors. However, the complex molecular mechanisms underscoring this role remain unresolved fully and continue to be the subject of research. In the context of water-use efficiency (WUE), a key indicator of a plant's ability to conserve water, this aspect links intrinsically with stomatal behavior. Given the pivotal role of stomata in modulating water loss, it can be argued that the complex mechanisms governing stomatal development and function will significantly influence a plant's WUE under different abiotic stress conditions. Addressing these calls for a concerted effort to strengthen plant adaptability through advanced, targeted research. In this vein, recent studies have illuminated how specific stressors trigger alterations in gene expression, orchestrating changes in stomatal pattern, structure, and opening. This reveals a complex interplay between stress stimuli and regulatory sequences of essential genes implicated in stomatal development, such as MUTE, SPCH, and FAMA. This review synthesizes current discoveries on the molecular foundations of stomatal development and behavior in various stress conditions and their implications for WUE. It highlights the imperative for continued exploration, as understanding and leveraging these mechanisms guarantee enhanced plant resilience amid an ever-changing climatic landscape.

An atypical heterotrimeric Gα and its interactome suggest an extra-large role in overcoming abiotic and biotic stress.

Canonical heterotrimeric G-proteins (G-proteins) are comprised of Gα, Gβ, and Gγ subunits. G-proteins regulate multiple crucial plant growth and development processes, incorporating environmental responses. Besides Gα, Gβ and Gγ, the discovery of atypical Gα subunits termed as extra-large G-proteins or extra-large GTP-binding proteins (XLGs) makes G-protein signaling unique in plants. The C-terminus of XLG shares similarities with the canonical Gα subunits; the N-terminus harbors a nuclear localization signal (NLS) and is rich in cysteine. The earlier explorations suggest XLG's role in flowering, the development of embryos and seedlings, root morphogenesis, stamen development, cytokinin-induced development, stomatal opening and regulation of rice grain filling. The XLGs are also known to initiate signaling cascades that prime plants against a variety of abiotic and biotic stresses. They are also engaged in controlling several agronomic parameters such as rice panicle length, grain filling, grain size, and biomass, highlighting their potential contribution to crop improvement. The present review explores the remarkable properties of non-canonical Gα subunits (XLGs) and reflects on the various developmental, abiotic and biotic stress signaling pathways controlled by them. Moreover, the bottleneck dilemma of how a tiny handful of XLGs control a multiplicity of stress-responsive activities is partially resolved in this review by addressing the interaction of XLGs with different interacting proteins. XLG proteins presented in this review can be exploited to gain access to highly productive and stress-tolerant plants.

Far-Red Light Affects Stomatal Opening and Evapotranspiration of Sweet Basil

Far-red light (FR; wavelength: 700–800 nm) is known for its effects on plant morphology and photosynthesis. However, its effects on stomatal responses and transpiration are not well understood. This study investigated the effects of FR on stomatal development and evapotranspiration in sweet basil grown under red, blue, and green (RGB) light-emitting diodes (LED). FR was provided for 10 days at 0, 30, 100, and 130 μmol·m−2·s−1 with the same base light (RGB ratio of 6:2:2; a photosynthetic photon flux density of 200 μmol·m−2·s−1). Evapotranspiration was measured using a load cell, and stomatal development was monitored microscopically. FR increased the height of sweet basil mostly due to the shade avoidance syndrome. The photosynthetic rate was not improved with FR, probably due to insufficient base light intensity. Despite similar leaf area and root growth, daily evapotranspiration increased with FR, resulting in higher water use. Although the stomatal density and guard cell area were similar across treatments, the stomatal aperture area was larger in plants with FR, thus increasing evapotranspiration. In conclusion, FR with the base RGB light intensity of 200 μmol·m−2·s−1 enhanced the evapotranspiration of sweet basil by regulating stomatal opening, but it did not enhance photosynthesis.

Low R:FR light ratio enhances calcium nitrate resistance and stomatal movement in tomato seedlings by regulating H2O2 accumulation

Secondary salinization is a major environmental factor that causes a stress response and growth inhibition in plants in protected agriculture. The positive effect of a low red to far-red light ratio (R:FR) in salt tolerance through antioxidant defense has been reported, while the underlying model remains obscure. In this study, we used physiological and genetic approaches to investigate the relationship between H2O2 signaling and low R:FR-induced salt tolerance and antioxidant capacity in tomato seedlings. This study found that low R:FR treatment with calcium nitrate stress (SL treatment) enhanced the growth of plants and increased the net photosynthetic rate 5 days after stress compared with a higher R:FR ratio and calcium nitrate stress (S treatment). With transcriptomic analysis of tomato leaves at 5 d, compared with CK, most of glutaredoxin genes and antioxidant enzymes were upregulated by S treatment, which were upregulated further by SL treatment. Compared to the S treatment, within 5 days, the H2O2 level was increased faster before 24 h and it was slowed down after 24 h by SL treatment, with less H2O2 accumulation at 5 d than that of S treatment. The enhancement of gene expression of RBOH genes were also shown at 24 h under SL. It was found that stomatal conductance followed the dynamic change of H2O2, with a rapid closure of stomata and decrease at 3 h and an increase after 9 h in SL treatment compared to S treatment, respectively. There was same trend of stomata opening degrees of tomato leaves observed by optical microscope. However, the inhibitor of H2O2 production (DPI pretreatment) weakened the positive effect of low R:FR on the regulation of stomatal movement. In addition, SL treatment increased the antioxidant enzyme activities and proline content and decreased the MDA content as compared to the S treatment, while the enhancement of ROS homeostasis was reduced by the DPI pretreatment. In conclusion, low R:FR improved redox homeostasis and stomatal status under calcium nitrate stress through H2O2 signaling, improving the adaptation of tomato seedlings to soil salinization stress.

Quantifying river water contributions to the transpiration of riparian trees along a losing river: lessons from stable isotopes and an iteration method

Abstract. River water plays a critical role in riparian plant water use and riparian ecosystem restoration along losing rivers (i.e., river water recharging underlying groundwater). How to quantify the contributions of river water to the transpiration of riparian plants under different groundwater levels and the related responses of plant water use efficiency is a great challenge. In this study, observations of stable isotopes of water (δ2H and δ18O), 222Rn, and leaf δ13C were conducted for the deep-rooted riparian weeping willow (Salix babylonica L.) in 2019 (dry year) and 2021 (wet year) along the Chaobai River in Beijing, China. We proposed an iteration method in combination with the MixSIAR model to quantify the river water contribution to the transpiration of riparian S. babylonica and its correlations with the water table depth and leaf δ13C. Our results demonstrated that riparian S. babylonica took up deep water (in the 80–170 cm soil layer and groundwater) by 56.5 % ± 10.8 %. River water recharging riparian deep water was an indirect water source and contributed 20.3 % of water to the transpiration of riparian trees near the losing river. Significantly increasing river water uptake (by 7.0 %) and decreasing leaf δ13C (by −2.0 ‰) of riparian trees were observed as the water table depth changed from 2.7 m in the dry year of 2019 to 1.7 m in the wet year of 2021 (p<0.05). The higher water availability probably promoted stomatal opening and thus increased transpiration water loss, leading to the decreasing leaf δ13C in the wet year compared to the dry year. The river water contribution to the transpiration of riparian S. babylonica was found to be negatively linearly correlated with the water table depth and leaf δ13C (p<0.01). The rising groundwater level may increase the water extraction from the groundwater and/or river and produce a consumptive river-water-use pattern of riparian trees, which can have an adverse impact on the conservation of both river flow and riparian vegetation. This study provides new insights into understanding the mechanisms of the water cycle in a groundwater–soil–plant–atmosphere continuum and managing water resources and riparian afforestation along losing rivers.

Plant Stomata: An Unrealized Possibility in Plant Defense against Invading Pathogens and Stress Tolerance.

Stomata are crucial structures in plants that play a primary role in the infection process during a pathogen's attack, as they act as points of access for invading pathogens to enter host tissues. Recent evidence has revealed that stomata are integral to the plant defense system and can actively impede invading pathogens by triggering plant defense responses. Stomata interact with diverse pathogen virulence factors, granting them the capacity to influence plant susceptibility and resistance. Moreover, recent studies focusing on the environmental and microbial regulation of stomatal closure and opening have shed light on the epidemiology of bacterial diseases in plants. Bacteria and fungi can induce stomatal closure using pathogen-associated molecular patterns (PAMPs), effectively preventing entry through these openings and positioning stomata as a critical component of the plant's innate immune system; however, despite this defense mechanism, some microorganisms have evolved strategies to overcome stomatal protection. Interestingly, recent research supports the hypothesis that stomatal closure caused by PAMPs may function as a more robust barrier against pathogen infection than previously believed. On the other hand, plant stomatal closure is also regulated by factors such as abscisic acid and Ca2+-permeable channels, which will also be discussed in this review. Therefore, this review aims to discuss various roles of stomata during biotic and abiotic stress, such as insects and water stress, and with specific context to pathogens and their strategies for evading stomatal defense, subverting plant resistance, and overcoming challenges faced by infectious propagules. These pathogens must navigate specific plant tissues and counteract various constitutive and inducible resistance mechanisms, making the role of stomata in plant defense an essential area of study.

Pengaruh Kolkisin pada Stomata Daun Dendrobium

This study aims to determine the effect of colchicine on the stomata of dendrobium orchids. This research method is quantitative. This research used 2 factorial RAK where the first factor was the variety treatment consisting of dendrobium venus purple algis (ALG) and dendrobium transient pink frederika (FRD). The second factor, namely the colchicine concentration treatment, consisted of control (0 ppm), 4000 ppm, 5000 ppm and 6000 ppm. The research parameters observed were stomata density, stomata length and width. The results showed that dendrobium orchid varieties FRD and ALG were treated with several concentrations of colchicine with the average parameters of open stomata, stomata density, length and width of somata not significantly different from each treatment or control. Colchicine still does not appear to have an effect on the stomata of the FRD and ALG varieties of dendrobium orchids. Based on observations of the stomata, the average length of the stomata at each concentration is still not classified as diploid because it is <1.25x the length of the control stomata. In conclusion, the observed parameters have no effect or are significantly different.
 
 Keywords: Dendrobium Orchid, Colchicine, Stomata

Suppression of SlDREB3 increases leaf ABA responses and promotes drought tolerance in transgenic tomato plants

Drought susceptibility is a major yield limiting factor in agricultural crops especially in hybrids/varieties that have been bred for high yields. We show that manipulation of the SlDREB3 gene in tomato alters ABA responses and thereby sensitivity of stomatal closure to ABA. SlDREB3 suppression lines show ABA hypersensitivity and rapid stomatal closure in response to ABA while over-expression lines show reduced sensitivity to ABA and open stomata even at high ABA levels with rapid water loss after 10 days of water stress. This is accompanied with high ROS levels and increased membrane damage due to senescence of leaves and drastically reduced survival in drought. The relative water content (RWC) of OEx lines is much reduced even when grown under well-watered conditions. In contrast, suppression lines show greater tolerance to water stress and almost complete survival to 10-day water stress. They show much reduced ROS levels, reduced membrane damage, higher RWC and reduced leaf water loss. These changes are associated with higher expression of ABA signalling pathway genes in suppression lines while these are highly reduced in OEx lines. The studies suggest that control of ABA signalling by SlDREB3 can help in withstanding severe drought.

Integrated Cytological, Physiological, and Transcriptome Analyses Provide Insight into the Albino Phenotype of Chinese Plum (Prunus salicina).

Albino seedlings that arise during seed reproduction can have a significant impact on plant growth and breeding. In this research, we present the first report of albino occurrences in the seed reproduction process of Prunus salicina and describe the cytological, physiological, and transcriptomic changes observed in albino seedlings. The albino seedlings which were observed in several plum cultivars exhibited abnormal chloroplast ultrastructure and perturbed stomatal structure. Compared to normal seedlings, the photosynthetic pigment contents in albino seedlings decreased by more than 90%, accompanied by significant reductions in several chlorophyll fluorescence parameters. Furthermore, substantially changed photosynthetic parameters indicated that the photosynthetic capacity and stomatal function were impaired in albino seedlings. Additionally, the activities of the antioxidant enzyme were drastically altered against the background of higher proline and lower ascorbic acid in leaves of albino seedlings. A total of 4048 differentially expressed genes (DEGs) were identified through transcriptomic sequencing, and the downregulated DEGs in albino seedlings were greatly enriched in the pathways for photosynthetic antenna proteins and flavonoid biosynthesis. GLK1 and Ftsz were identified as candidate genes responsible for the impaired chloroplast development and division in albino seedlings. Additionally, the substantial decline in the expression levels of examined photosystem-related chloroplast genes was validated in albino seedlings. Our findings shed light on the intricate physiological and molecular mechanisms driving albino plum seedling manifestation, which will contribute to improving the reproductive and breeding efforts of plums.

Maize MITOGEN-ACTIVATED PROTEIN KINASE 20 mediates high-temperature-regulated stomatal movement.

High temperature induces stomatal opening; however, uncontrolled stomatal opening is dangerous for plants in response to high temperature. We identified a high-temperature sensitive (hts) mutant from the ethyl methane sulfonate (EMS)-induced maize (Zea mays) mutant library that is linked to a single base change in MITOGEN-ACTIVATED PROTEIN KINASE 20 (ZmMPK20). Our data demonstrated that hts mutants exhibit substantially increased stomatal opening and water loss rate, as well as decreased thermotolerance, compared to wild-type plants under high temperature. ZmMPK20-knockout mutants showed similar phenotypes as hts mutants. Overexpression of ZmMPK20 decreased stomatal apertures, water loss rate, and enhanced plant thermotolerance. Additional experiments showed that ZmMPK20 interacts with MAP KINASE KINASE 9 (ZmMKK9) and E3 ubiquitin ligase RPM1 INTERACTING PROTEIN 2 (ZmRIN2), a maize homolog of Arabidopsis (Arabidopsis thaliana) RIN2. ZmMPK20 prevented ZmRIN2 degradation by inhibiting ZmRIN2 self-ubiquitination. ZmMKK9 phosphorylated ZmMPK20 and enhanced the inhibitory effect of ZmMPK20 on ZmRIN2 degradation. Moreover, we employed virus-induced gene silencing (VIGS) to silence ZmMKK9 and ZmRIN2 in maize and heterologously overexpressed ZmMKK9 or ZmRIN2 in Arabidopsis. Our findings demonstrated that ZmMKK9 and ZmRIN2 play negative regulatory roles in high-temperature-induced stomatal opening. Accordingly, we propose that the ZmMKK9-ZmMPK20-ZmRIN2 cascade negatively regulates high-temperature-induced stomatal opening and balances water loss and leaf temperature, thus enhancing plant thermotolerance.