Auxin Concentration Research Articles

MtPIN4 plays critical roles in amino acid biosynthesis and metabolism of seed in Medicago truncatula.

The regulation of seed development is critical for determining crop yield. Auxins are vital phytohormones that play roles in various aspects of plant growth and development. However, its role in amino acid biosynthesis and metabolism in seeds is not fully understood. In this study, we identified a mutant with small seeds through forward genetic screening in Medicago truncatula. The mutated gene encodes MtPIN4, an ortholog of PIN1. Using molecular approaches and integrative omics analyses, we discovered that auxin and amino acid content significantly decreased in mtpin4 seeds, highlighting the role of MtPIN4-mediated auxin distribution in amino acid biosynthesis and metabolism. Furthermore, genetic analysis revealed that the three orthologs of PIN1 have specific and overlapping functions in various developmental processes in M. truncatula. Our findings emphasize the significance of MtPIN4 in seed development and offer insights into the molecular mechanisms governing the regulation of seed size in crops. This knowledge could be applied to enhance crop quality by targeted manipulation of seed protein regulatory pathways.

A novel semi-dominant allele of the transmembrane NAC transcription factor ZmNTL2 reduces the size of multiple maize organs

Maize plant architecture influences planting density and, in turn, grain yield. Most of the plant architecture-related traits can be described as organ size. We describe a miniature maize mutant, Tiny plant 4 (Tip4), which exhibits reduced size of multiple organs and exhibits a semi-dominant monofactorial inheritance characteristic. Positional cloning confirmed that a 4-bp deletion in the NAC TF with transmembrane motif 1-Like (NTL) gene ZmNTL2, denoted as ZmNTL2Δ, confers the Tip4 mutation. qRT-PCR showed that ZmNTL2 was expressed in all tested tissues. ZmNTL2 functions as a transcriptional activator and is located in both the nucleus and biomembranes. The mutation does not affect the mRNA abundance of ZmNTL2 locus, but it does result in the loss of transmembrane domain and confines the ZmNTL2Δ protein to the nucleus. Knocking out ZmNTL2 has no effect on maize organ size development, indicating that the 4-bp deletion might be a gain-of-function mutation in organ size regulation. Combining transcriptome sequencing with cytokinin and auxin content determination suggests that the decreased organ size may be possibly mediated by changes in hormone homeostasis.

Regulatory Mechanisms of Strigolactones on the Development of Lateral Branches in Cucumber

Cucumber (Cucumis sativus L.) belongs to the cucumber genus of the Cucurbitaceae family, and the selection of cultivars with minimal or no lateral branches can enhance the cultivation management efficiency. The growth of lateral branches is inhibited by strigolactone. To investigate the regulatory mechanism of strigolactone on the lateral branch development in cucumber, the cultivar LZ1 exhibiting multiple lateral branches was selected as the experimental material. The axillae of the plants were infiltrated with 1, 5, and 10 μmol·L−1 germination releaser 24 (GR24) at the four- to five-leaf stage. It was identified that 1 μmol·L−1 GR24 exhibited the most potent inhibitory effect on cucumber lateral branches. Additionally, exogenous strigolactone decreased the auxin content in the apical bud and axillae and increased the auxin content in the stem. This inhibited polar auxin transport in the axillary bud and promoted polar auxin transport in the apical bud. The content of strigolactone in the axilla region of cucumbers was elevated, whereas the synthesis and expression of cytokinin in the same area were reduced. A low concentration of GR24 induced the expression of cucumber branched 1 (csbrc1), whereas a high concentration of GR24 downregulated the expression of cucumber lateral suppressor (cscls) and blind (csblind), which inhibited the growth of cucumber lateral branches.

Potato (Solanum tuberosum L.) Planlet Acclimatization on Various Auxin Concentrations and Growing Media

The provision of quality potato seeds is a problem faced by farmers. Tissue culture propagation is an effort to increase the availability of quality seeds. The success of tissue culture is influenced by the ability to control environmental conditions, growth regulators, and growing media at the acclimatization stage. The research aims to determine the interaction between the use of auxin concentrations and the planting medium and to obtain the appropriate concentration of auxin and planting medium for potato acclimatization. The research used a split-plot design with 2 factors and 3 replications. The main plot is the auxin concentration consisting of 3 levels; 1 ppm, 2 ppm, and 3 ppm. Subplots are planting media consisting of 3 levels; husk charcoal:vermicompost, cocopeat:vermicompost, and husk charcoal:cocopeat:vermicompost. Data were analyzed using ANOVA and followed by DMRT at a 5% level. The results showed that there was an interaction between the treatment of 3 ppm IAA concentration and the planting medium of husk charcoal:cocopeat:vermicompost on the plant height parameter 4 WAP. The IAA concentration of 3 ppm was better than the concentration of 1 ppm in the parameter number of leaves 8 WAP. The growing media of husk charcoal:cocopeat:vermicompost was better than the growing medium of charcoal husk:vermicompost on the parameters of plant height 8 WAP, number of leaves 8 WAP, leaf length and leaf width 8 WAP.

In vitro multiplication of strawberry in various types and concentrations of cytokinins and auxins

In vitro multiplication of strawberry in various types and concentrations of cytokinins and auxins

Establishment of callus cultures and quantification of Caffeic acid using HPTLC from Desmodium gangeticum (L.)

Desmodium gangeticum (L.) belonging to family Fabaceae is an economically important medicinal plant which isutilised in Dashmoolarishta. Various bioactive compounds have been isolated from whole plant and roots, and one of them is an important phenolic compound – caffeic acid (CA). This phenolic acid and its derivatives have antioxidant, anti-inflammatory, anticarcinogenic and hepatocarcinoma, a highly aggressive and causing considerable mortality across the world. In the present study, leaf explants were placed on MS medium fortified with different concentration of cytokinin (BA/Kn) and auxin (IAA/NAA) for establishing callus cultures. MS medium fortified with BA (20 µM) and IAA (2 µM) was optimised for the same. Methanolic extracts of in vivo leaf sample (DG1) and in vitro sample (leaf derived callus) (DG2) were assessed for CA quantification using HPTLC. Thus, the chemical fingerprint that was obtained, confirmed that DG 2 of D. gangeticum exhibited the potency to synthesise more amount of CA (316 ± 7.5 µg/g DW) in comparison to DG1 which was 194 ± 2.3 µg/g DW.

Light Supplementation in Pitaya Orchards Induces Pitaya Flowering in Winter by Promoting Phytohormone Biosynthesis.

The interaction between light and phytohormones is crucial for plant growth and development. The practice of supplementing light at night during winter to promote pitaya flowering and thereby enhance yield has been shown to be crucial and widely used. However, it remains unclear how supplemental winter light regulates phytohormone levels to promote flowering in pitaya. In this study, through analyzing the transcriptome data of pitaya at four different stages (NL, L0, L1, L2), we observed that differentially expressed genes (DEGs) were mainly enriched in the phytohormone biosynthesis pathway. We further analyzed the data and found that cytokinin (CK) content first increased at the L0 stage and then decreased at the L1 and L2 stages after supplemental light treatment compared to the control (NL). Gibberellin (GA), auxin (IAA), salicylic acid (SA), and jasmonic acid (JA) content increased during the formation of flower buds (L1, L2 stages). In addition, the levels of GA, ethylene (ETH), IAA, and abscisic acid (ABA) increased in flower buds after one week of development (L2f). Our results suggest that winter nighttime supplemental light can interact with endogenous hormone signaling in pitaya, particularly CK, to regulate flower bud formation. These results contribute to a better understanding of the mechanism of phytohormone interactions during the induction of flowering in pitaya under supplemental light in winter.

ERECTA Modulates Seed Germination and Fruit Development via Auxin Signaling in Tomato.

Tomato (Solanum lycopersicum) breeding for improved fruit quality emphasizes selecting for desirable taste and characteristics, as well as enhancing disease resistance and yield. Seed germination is the initial step in the plant life cycle and directly affects crop productivity and yield. ERECTA (ER) is a receptor-like kinase (RLK) family protein known for its involvement in diverse developmental processes. We characterized a Micro-Tom EMS mutant designated as a knock-out mutant of sler. Our research reveals that SlER plays a central role in controlling critical traits such as inflorescence development, seed number, and seed germination. The elevation in auxin levels and alterations in the expression of ABSCISIC ACID INSENSITIVE 3 (ABI3) and ABI5 in sler seeds compared to the WT indicate that SlER modulates seed germination via auxin and abscisic acid (ABA) signaling. Additionally, we detected an increase in auxin content in the sler ovary and changes in the expression of auxin synthesis genes YUCCA flavin monooxygenases 1 (YUC1), YUC4, YUC5, and YUC6 as well as auxin response genes AUXIN RESPONSE FACTOR 5 (ARF5) and ARF7, suggesting that SlER regulates fruit development via auxin signaling.

Zinc-Enhanced Regulation of the Ginkgo biloba L. Response and Secondary Metabolites

Ginkgo biloba L. leaves are rich in secondary metabolites with important medicinal values; to increase their contents, foliar spraying of micronutrients is a potential strategy. Zinc, a multifunctional element, has a significant impact on the content of secondary metabolites in other plants, but relevant research into ginkgo is still lacking. In our study, different spraying time and concentration strategies were used to investigate the effects of zinc sulfate (ZnSO4) on physiological indicators and secondary metabolites of 2-year-old ginkgo. The results demonstrated that ZnSO4 could increase the contents of hydrogen peroxide, abscisic acid, and free amino acids in ginkgo leaves. It also enhances the antioxidant enzyme activity of ginkgo leaves, decreases the content of plant auxin, and ultimately facilitates the accumulation of ginkgo terpene lactones (TTL). Spraying ZnSO4 in June resulted in a more significant increase in the contents of TTL and flavonoids compared to spraying in August. After spraying 12 mmol/L ZnSO4 in June, the contents of TTL and flavonoids in ginkgo leaves were significantly elevated by 35.95% and 24.30%, respectively, compared to those in the CK (p < 0.05). The contents of ginkgolide A, B, and C were notably increased by 45.93%, 46.56%, and 74.29%, respectively, compared to those in the CK (p < 0.05). Therefore, our study suggests that the optimal timing for spraying ZnSO4 on ginkgo is in June, with a recommended concentration of 12 mmol/L. Our study provides a theoretical basis for the accumulation of secondary metabolites in ginkgo and guides the production of its leaf-utilization plantations.

New perspectives on radial profiles of specific gravity in North American conifers

North American conifers exhibit three radial specific gravity (SG) patterns (Type 1, 2, and 3), which balance hydraulic and mechanical requirements. Type 1 and 2 patterns (Pinaceae) have low SG and high microfibril angle (MFA) corewood ensuring compliance, whereas in outerwood high SG/low MFA provide stiffness and strength resisting bending. Hydraulically, corewood, especially in Type 2 species, is resistant to embolism, whereas outerwood has higher specific conductivity. Cupressaceae (Type 3) have hydraulically very efficient, low SG outerwood, facilitating rapid growth. Corewood is flexible, whereas outerwood is mechanically weak and compensated for by more conical stems and durable heartwood (which prevents Brazier buckling). Radially earlywood (EW) decreases, and latewood (LW) increases for all types, whereas %latewood (%LW) increases (Type 1), decreases, then increases (Type 2) and decreases (Type 3). Ring SG increases when increasing LW SG and %LW are sufficient to counteract decreasing EW SG. Shade tolerance, crown recession, hormone gradients, and environmental variation affect patterns. Auxin concentration decreases with increasing distance from juvenile foliage slowing cell division, concomitantly gibberellin concentration (lignification) and carbohydrates (cell wall thickening) increase, producing higher %LW. Across a species range regions receiving relatively high summer rainfall have trees with higher %LW (by ring).

Exploring somatic embryogenesis in Ajuga multiflora Bunge: Profiling lipophilic metabolites via HPLC, GC-FID, and GCMS– analysis

The present study aims to assess the effect of different concentrations of auxins and combinations of plant growth regulators (PGRs), specifically auxin and cytokinin, on somatic embryogenesis in Ajuga multiflora. We also aim to compare the lipophilic metabolite profiles, such as carotenoids (CAs), fatty acids (FAs), phytosterols (PSs), and tocopherols (TPs), in globular somatic embryos (SEs), germinated SEs, and shoots of SEs derived plantlets. This assessment is carried out utilizing high performance liquid chromatography, gas chromatography-flame-ionization detection, and gas chromatography–mass spectrometry techniques. The results reveal that the application of 2,4-dichlorophenoxyacetic acid (2,4-D) had the most significant impact on somatic embryogenesis, inducing both SE initiation (34.4%) and the number of SEs (3.5) per explant. Among the explants used, leaf explants were found to be the most effective for SE induction (SEI). Additionally, the study explores the combined effect of 2,4-D and cytokinins (N6-benzyladenine, N6-BA, or 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea, TDZ) on somatic embryogenesis, highlighting optimal conditions for SEI percentages and the number of SEs per explant. The maximum SE induction rate (100%) and the number of SEs (45.9) per leaf explant were obtained on an SEI medium with 30 µM of 2,4-D and 2.3 µM of TDZ. The maturation and conversion of SEs were also examined, emphasizing the role of GA3 in achieving the highest conversion percentage (94.0 ± 2.7 at 0.8 µM GA3). Furthermore, the study details the biochemical composition during various stages of somatic embryogenesis, including CAs, TPs, PSs, and FAs. Globular SEs displayed comparatively lower concentrations of CAs than their germinated counterparts and shoots from SE-derived plantlets, while the total PSs content remained relatively consistent across all stages. Conversely, fatty acids tended to accumulate more in globular SEs, with the exception of α-Linolenic acid. These findings provide valuable insights into the optimization of somatic embryogenesis protocols in A. multiflora, with implications for plant tissue culture, regeneration and lipophilic metabolites production.

Bulked Segregant RNA-Seq Reveals Different Gene Expression Patterns and Mutant Genes Associated with the Zigzag Pattern of Tea Plants (Camellia sinensis).

The unique zigzag-patterned tea plant is a rare germplasm resource. However, the molecular mechanism behind the formation of zigzag stems remains unclear. To address this, a BC1 genetic population of tea plants with zigzag stems was studied using histological observation and bulked segregant RNA-seq. The analysis revealed 1494 differentially expressed genes (DEGs) between the upright and zigzag stem groups. These DEGs may regulate the transduction and biosynthesis of plant hormones, and the effects on the phenylpropane biosynthesis pathways may cause the accumulation of lignin. Tissue sections further supported this finding, showing differences in cell wall thickness between upright and curved stems, potentially due to lignin accumulation. Additionally, 262 single-nucleotide polymorphisms (SNPs) across 38 genes were identified as key SNPs, and 5 genes related to zigzag stems were identified through homologous gene function annotation. Mutations in these genes may impact auxin distribution and content, resulting in the asymmetric development of vascular bundles in curved stems. In summary, we identified the key genes associated with the tortuous phenotype by using BSR-seq on a BC1 population to minimize genetic background noise.

Effect of Leaf Pruning and Additional Fertilizer on Growth and Young Pods Yield of Winged Beans

Winged bean (Psophocarpus tetragonolobus L.) exhibits luxuriant foliage, making leaf pruning essential to enhance sunlight interception. Additionally, supplementing with additional fertilizer helps offset the impact of gradual harvesting. Therefore, this research aimed to determine the effect of leaf pruning and additional fertilizer on the growth and yield parameter of winged beans in the Institut Pertanian Bogor (IPB) experimental station at Leuwikopo, IPB University, Bogor, Indonesia. A randomized complete block design was used with two factors and three replications, namely leaf pruning intensities (0, 15, and 30% leaf pruning) and rates of additional fertilizer (0, 6.25, 12.5, and 18.5 g NPK 16-16-16/plant). The observed variables were plant height, leaf number, root length, leaf nutrient, auxin content, nutrient uptake, and young pods yield. The findings revealed that the interaction of pruning intensities and additional fertilizer rates significantly influenced leaf number and root length. Specifically, plants receiving a treatment combination without pruning and 6.25 g of additional fertilizer/plant exhibited the highest leaf number. In contrast, those subjected to 15% leaf pruning showed the greatest root length. Leaf nutrient levels, auxin content, and nutrient uptake exhibited noticeable improved with the addition of fertilizer. Meanwhile, a higher phosphorus and organic carbon content was observed in the 15% pruning treatment, and the young pods yield were not affected because the Fairuz variety reached its potential yield. Based on the results, the most recommended treatment is a combination without leaf pruning, supplemented with 6.25 g of additional fertilizer/plant.

VEGETATIVE PROPAGATION FROM SHOOT CUTTINGS OF MATURE ROSEWOOD TREES (ANIBA ROSAEODORA DUCKE)

The production of seedlings by cuttings is an alternative to reconcile exploration and conservation of Rosewood (Aniba rosaeodora Ducke). In this study, our objective was to evaluate the rooting of cuttings from epicormic shoots of adult rosewood strains, through substrate tests, auxin concentrations, and cutting types, as well as to describe the anatomical process of the formation of adventitious roots. We carried out two experiments: E1 - substrate test (sand [A], vermiculite [V], and A+V) and concentrations of indole butyric acid (IBA) via talc (0.0; 1.5; 3.0; 6 .0 g kg-1); E2 – evaluation of the type of cutting: apical, intermediate, basal and regrowth; in addition to anatomical analyzes on samples of rooted cuttings. In the experiments, the variables survival (%), rooting (%), number of roots, and length of the largest root (cm) were evaluated. In E2, shoots (%), number of shoots, length of the largest shoot (cm), and callosity (%) were added. The rooting at 3.0 g kg-1 IBA was better than the control and vermiculite as a substrate was superior to sand. Even without interaction, auxin showed a tendency for better rooting when used with one of the vermiculite substrates. Among the types of cuttings, the regrowth was superior for most variables, differing from the others in terms of sprouting and callosity, while the basal was inferior in the concentration of total carbohydrates and starch.

Factors influencing Agrobacterium-mediated genetic transformation efficiency in bread wheat (Triticum aestivum L.)

Assessment of the efficiency of Agrobacterium tumefaciens mediated transformation in four bread wheat varieties was focused and upon optimization of experiments done to obtain tangible results. The four varieties, Fielder, Navojoa, Baj and Kachu/saul, were transformed with optimized protocols and randomly selected from a selection medium amalgamated with phosphinothricin (Glufosinate). Initially, the variety Fielder has proceeded with 36 different concentrations of synthetic auxins 2,4-D and picloram as 36 treatments. The treatment 30 (48 μg of 2,4-D and 64 μg of picloram) has shown higher efficiency and is comparable in terms of the three traits studied. Additionally, antioxidants and growth regulators were adjusted to obtain better results towards reasonable transformation frequency. Additional varieties were also tested and selected against the selectable marker PPT based on the optimization for the variety Fielder. Selected genotypes were subjected for gusA or Bar gene PCR amplification. The result revealed the frequency of transgenesis in the range of 60 to 70% with the varieties studied. However, the whole experiment needs further repetitions for confirmatory results. Transgenic genotypes of the Fielder variety showed moderate to strong GUS expression in leaves, anthers, seeds, seed coats, and roots compared to non-transgenic control plant tissues. PPT leaf painting assay showed the lack of necrosis on the painted area of leaves in transgenic genotypes compared to the non-transgenic ones.

Characterization and Transcriptome Analysis Reveal Exogenous GA3 Inhibited Rosette Branching via Altering Auxin Approach in Flowering Chinese Cabbage

Branching is an important agronomic trait that is conducive to plant architecture and yield in flowering Chinese cabbage. Plant branching is regulated by a complex network mediated by hormones; gibberellin (GA) is one of the important hormones which is involved in the formation of shoot branching. Research on the regulatory mechanism of GA influencing rosette branch numbers is limited for flowering Chinese cabbage. In this study, the exogenous application of 600 mg/L GA3 effectively inhibited rosette branching and promoted internode elongation in flowering Chinese cabbage. RNA-Seq analysis further found that these DEGs were significantly enriched in ‘the plant hormone signal transduction’ pathways, and auxin-related genes were significantly differentially expressed between MB and MB_GA. The upregulation of auxin (AUX) and the upregulation of auxin/indole-3-acetic acid (AUX/IAA), as well as the downregulation of SMALL AUXIN-UPREGULATED RNA (SAUR), were found in the negative regulation of the rosette branching. The qRT-PCR results showed that the expression of AUX/IAA and SAUR from IAA gene family members were consistent with the results of transcriptome data. Phytohormone profiling by targeted metabolism revealed that endogenous auxin contents were significantly increased in MB_GA. Transcriptome and metabolome analysis clarified the main plant hormones and genes underlying the rosette branching in flowering Chinese cabbage, confirming that auxin could inhibit rosette branching. In this regard, the results present a novel angle for revealing the mechanism of gibberellin acting on the branching architecture in flowering Chinese cabbage.

CpEXO70A1/3 regulate root development via affecting auxin accumulation in Chinese herbal plant Codonopsis pilosula

Codonopsis pilosula is an herbal plant that belongs to the Campanulaceae family, the dried roots (Dangshen) of which have long been used in traditional Chinese medicine to treat dyspepsia, hypertension, and hyperglycemia. The development of roots is very crucial for producing high-quality Dangshen due to their main medicinal components. However, i the regulation mechanism of root development remains limited. Here, we identified two subunits CpEXO70A1 and CpEXO70A3, of the evolutionarily conserved exocyst complex in C. pilosula. Either CpEXO70A1 or CpEXO70A3 responded to IAA, ABA, and drought treatments. The subcellular localization and GUS-staining assay indicated that CpEXO70A1 and CpEXO70A3 were located in the plasma membrane and exhibited temporal and spatial expression patterns. Overexpression or CRISPR knock-out of the two genes led to reduced biomass in C. pilosula hairy roots, correlating with changes in auxin concentration. Besides, a model predicting the impact of auxin-PIN-EXO70A3 onon root growth and development was proposed. Our study aims to enhance Dangshen yield through molecular breeding in the future.

Biomass ash as soil fertilizers: Supercharging biomass accumulation by shifting auxin distribution

Growing quantities of biomass ashes (phyto-ashs) are currently produced worldwide due to the increasing biomass consumption in energy applications. Utilization of phyto-ash in agriculture is environmentally friendly solution. However, mechanisms involving the coordination of carbon metabolism and distribution in plants and soil amendment are not well known. In the present study, tobacco plants were chemically-fertilized with or without 2‰ phyto-ash addition. The control had sole chemical fertilizer; for two phyto-ash treatments, the one (T1) received comparable levels of nitrogen, phophorus, and potassium from phyto-ash and fertilizers as the control and another (T2) had 2‰ of phyto-ash and the same rates of fertilizers as the control. Compared with the control, phyto-ash addition improved the soil pH from 5.94 to about 6.35; T2 treatment enhanced soil available potassium by 30% but no difference of other elements was recorded among three treatments. Importantly, bacterial (but not fungal) communities were significantly enriched by phyto-ash addition, with the rank of richness as: T2 > T1 > control. Consistent with amelioration of soil properties, phyto-ash promoted plant growth through enlarged leaf area and photosynthesis and induced outgrowth of lateral roots (LRs). Interestingly, increased auxin content was recorded in 2nd and 3rd leaves and roots under phyto-ash application, also with the rank level as T2 > T1 > control, paralleling with higher transcripts of auxin synthetic genes in the topmost leaf and stronger [3H]IAA activity under phyto-ash addition. Furthermore, exogenous application of analog exogenous auxin (NAA) restored leaf area, photosynthesis and LR outgrowth to the similar level as T2 treatment; conversely, application of auxin transport inhibitor (NPA) under T2 treatment retarded leaf and root development. We demonstrated that phyto-ash addition improved soil properties and thus facilitated carbon balance within plants and biomass accumulation in which shifting auxin distribution plays an important role.

Multi-hormonal analysis and aquaporins regulation reveal new insights on drought tolerance in grapevine

Disentangling the factors that foster the tolerance to water stress in plants could provide great benefits to crop productions. In a two-year experiment, two new PIWI (fungus resistant) grapevine varieties, namely Merlot Kanthus and Sauvignon Kretos (Vitis hybrids), grown in the field, were subjected to two different water regimes: weekly irrigated (IR) or not irrigated (NIR) for two months during the summer. The two varieties exhibited large differences in terms of performance under water-limiting conditions. In particular, Merlot Kanthus strongly decreased stem water potential (Ψs) under water shortage and Sauvignon Kretos maintained higher Ψs values accompanied by generally high stomatal conductance and net carbon assimilation, regardless of the treatment. We hypothesized differences in the hormonal profile that mediate most of the plant responses to stresses or in the regulation of the aquaporins that control the water transport in the leaves. In general, substantial differences were found in the abundance of different hormonal classes, with Merlot Kanthus reporting higher concentrations of cytokinins while Sauvignon Kretos higher concentrations of auxins, jasmonate and salicylic acid. Interestingly, under water stress conditions ABA modulation appeared similar between the two cultivars, while other hormones were differently modulated between the two varieties. Regarding the expression of aquaporin encoding genes, Merlot Kanthus showed a significant downregulation of VvPIP2;1 and VvTIP2;1 in leaves exposed to water stress. Both genes have probably a role in influencing leaf conductance, and VvTIP2;1 has been correlated with stomatal conductance values. This evidence suggests that the two PIWI varieties are characterized by different behaviour in response to drought. Furthermore, the findings of the study may be generalized, suggesting the involvement of a complex hormonal cross-talk and aquaporins in effectively influencing plant performance under water shortage.

Knockout of endoplasmic reticulum-localized molecular chaperone HSP90.7 impairs seedling development and cellular auxin homeostasis in Arabidopsis.

The Arabidopsis endoplasmic reticulum-localized heat shock protein HSP90.7 modulates tissue differentiation and stress responses; however, complete knockout lines have not been previously reported. In this study, we identified and analyzed a mutant allele, hsp90.7-1, which was unable to accumulate the HSP90.7 full-length protein and showed seedling lethality. Microscopic analyses revealed its essential role in male and female fertility, trichomes and root hair development, proper chloroplast function, and apical meristem maintenance and differentiation. Comparative transcriptome and proteome analyses also revealed the role of the protein in a multitude of cellular processes. Particularly, the auxin-responsive pathway was specifically downregulated in the hsp90.7-1 mutant seedlings. We measured a much-reduced auxin content in both root and shoot tissues. Through comprehensive histological and molecular analyses, we confirmed PIN1 and PIN5 accumulations were dependent on the HSP90 function, and the TAA-YUCCA primary auxin biosynthesis pathway was also downregulated in the mutant seedlings. This study therefore not only fulfilled a gap in understanding the essential role of HSP90 paralogs in eukaryotes but also provided a mechanistic insight on the ER-localized chaperone in regulating plant growth and development via modulating cellular auxin homeostasis.