Regulation Of Root Development Research Articles

A Study on the Functional Identification of Overexpressing Winter Wheat Expansin Gene TaEXPA7-B in Rice under Salt Stress

Expansin is a cell wall relaxant protein that is common in plants and directly or indirectly participates in the whole process of plant root growth, development and morphogenesis. A well-developed root system helps plants to better absorb water and nutrients from the soil while effectively assisting them in resisting osmotic stress, such as salt stress. In this study, we observed and quantified the morphology of the roots of Arabidopsis overexpressing the TaEXPAs gene obtained by the research group in the early stage of development. We combined the bioinformatics analysis results relating to EXPA genes in five plants and identified TaEXPA7-B, a member of the EXPA family closely related to root development in winter wheat. Subcellular localization analysis of the TaEXPA7-B protein showed that it is located in the plant cell wall. In this study, the TaEXPA7-B gene was overexpressed in rice. The results showed that plant height, root length and the number of lateral roots of rice overexpressing the TaEXPA7-B gene were significantly higher than those of the wild type, and the expression of the TaEXPA7-B gene significantly promoted the growth of lateral root primordium and cortical cells. The plants were treated with 250 mM NaCl solution to simulate salt stress. The results showed that the accumulation of osmotic regulators, cell wall-related substances and the antioxidant enzyme activities of the overexpressed plants were higher than those of the wild type, and they had better salt tolerance. This paper discusses the effects of winter wheat expansins in plant root development and salt stress tolerance and provides a theoretical basis and relevant reference for screening high-quality expansin regulating root development and salt stress resistance in winter wheat and its application in crop molecular breeding.

OsNAC121 regulates root development, tillering, panicle morphology, and grain filling in rice plant.

Transcription factors in coordination with phytohormones form an intricate regulatory network modulating vital cellular mechanisms like development, growth and senescence in plants. In this study, we have functionally characterized the transcription factor OsNAC121 by developing gene silencing and overexpressing transgenic rice plants, followed by detailed analyses of the plant architecture. Transgenic lines exhibited remodelling in crown root development, lateral root structure and density, tiller height and number, panicle and grain morphologies, underpinning the imbalanced auxin: cytokinin ratio due to perturbed auxin transportation. Application of cytokinin, auxin and abscisic acid increased OsNAC121 gene expression nearly 17-, 6- and 91-folds, respectively. qRT-PCR results showed differential expressions of auxin and cytokinin pathway genes, implying their altered levels. A 47-fold higher expression level of OsNAC121 during milky stage in untransformed rice, compared to 14-day old shoot tissue, suggests its crucial role in grain filling; as evidenced by a large number of undeveloped grains produced by the gene silenced lines. Crippled gravitropic response by the transgenic plants indicates their impaired auxin transport. Bioinformatics revealed that OsNAC121 interacts with co-repressor (TOPLESS) proteins and forms a part of the inhibitor complex OsIAA10, an essential core component of auxin signalling pathway. Therefore, OsNAC121 emerges as an important regulator of various aspects of plant architecture through modulation of crosstalk between auxin and cytokinin, altering their concentration gradient in the meristematic zones, and consequently modifying different plant organogenesis processes.

Overexpression of the peroxidase gene ZmPRX1 increases maize seedling drought tolerance by promoting root development and lignification

Drought is a main abiotic stress factor hindering plant growth, development, and crop productivity. Therefore, it is crucial to understand the mechanisms by which plants cope with drought stress. Here, the function of the maize peroxidase gene ZmPRX1 in drought stress tolerance was investigated by measurement of its expression in response to drought treatment both in a ZmPRX1 overexpression line and a mutant line. The higher root lignin accumulation and seedling survival rate of the overexpression line than that of the wild type or mutant support a role for ZmPRX1 in maize drought tolerance by regulating root development and lignification. Additionally, yeast one-hybrid, Dule luciferase and ChIP-qPCR assays showed that ZmPRX1 is negatively regulated by a nuclear-localized ZmWRKY86 transcription factor. The gene could potentially be used for breeding of drought-tolerant cultivars.

Genome-Wide and Transcriptome-Wide Association Analysis Identifies qRS-6D and Its Candidate Genes Regulating Root Development of Wheat Seedlings

Wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide, and its production is challenged by global climate change and a shortage of resources. The root system plays a vital role in uptaking water and nutrients and sensing soil environmental signals, and it has great potential to improve the final yield and stress tolerance of wheat. In order to further explore the genes regulating root development, this study focused on qRS-6D, located on chromosome 6D and spanning from 462,701,391 to 465,068,943, which was significantly associated with the total root length, root volume, root surface, and root fresh weight in our previous GWAS analysis. Firstly, its genetic effects were validated using an F6 segregating population by comparing the root-related traits of homologous lines harboring the alternative haplotypes of this QTL. Then, the number of causal genes of this QTL was narrowed down to four with a transcriptome-wide association study. Additionally, qRS-6D has been demonstrated to have genetic effects on several yield- (kernel length, kernel width, and thousand-kernel weight) and plant structure-related traits (plant height, peduncle length, total tiller number, productive tiller number, flag leaf length, and flag leaf angle). Relatively, the frequency of the favorable haplotype increased with the wheat breeding practice. This study provides a reliable genetic locus to improve root development and structure and evaluate its application potential in wheat breeding improvement.

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.

AtHD2D is involved in regulating lateral root development and participates in abiotic stress response in Arabidopsis

Roots are essential to terrestrial plants, as their growth and morphology are crucial for plant development. The growth of the roots is affected and regulated by several internal and external environmental signals and metabolic pathways. Among them, chromatin modification plays an important regulatory role. In this study, we explore the potential roles of the histone deacetylase AtHD2D in root development and lay the foundation for further research on the biological processes and molecular mechanisms of AtHD2D in the future. Our study indicates that AtHD2D affects the root tip microenvironment homeostasis by affecting the gene transcription levels required to maintain the root tip microenvironment. In addition, we confirmed that AtHD2D is involved in regulating Arabidopsis lateral root development and further explained the possible role of AtHD2D in auxin-mediated lateral root development. AtHD2D can effectively enhance the resistance of Arabidopsis thaliana to abiotic stress. We believe that AtHD2D is involved in coping with abiotic stress by promoting the development of lateral roots. Overexpression of AtHD2D promotes the accumulation of reactive oxygen species (ROS) in roots, indicating that AtHD2D is also involved in developing lateral roots mediated by ROS. Previous studies have shown that the overexpression of AtHD2D can effectively enhance the resistance of Arabidopsis thaliana to abiotic stress. Based on our data, we believe that AtHD2D participates in the response to abiotic stress by promoting the development of lateral roots. AtHD2D-mediated lateral root development provides new ideas for studying the mechanism of HDAC protein in regulating root development.

Genome-Wide Identification and Analysis of the Aux/IAA Gene Family in Panax ginseng: Evidence for the Role of PgIAA02 in Lateral Root Development.

Panax ginseng C. A. Meyer (Ginseng) is one of the most used traditional Chinese herbal medicines, with its roots being used as the main common medicinal parts; its therapeutic potential has garnered significant attention. AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) is a family of early auxin-responsive genes capable of regulating root development in plants through the auxin signaling pathway. In the present study, 84 Aux/IAA genes were identified from the ginseng genome and their complexity and diversity were determined through their protein domains, phylogenetic relationships, gene structures, and cis-acting element predictions. Phylogenetic analyses classified PgIAA into six subgroups, with members in the same group showing greater sequence similarity. Analyses of interspecific collinearity suggest that segmental duplications likely drove the evolution of PgIAA genes, followed by purifying selection. An analysis of cis-regulatory elements suggested that PgIAA family genes may be involved in the regulation of plant hormones. RNA-seq data show that the expression pattern of Aux/IAA genes in Ginseng is tissue-specific, and PgIAA02 and PgIAA36 are specifically highly expressed in lateral, fibrous, and arm roots, suggesting their potential function in root development. The PgIAA02 overexpression lines exhibited an inhibition of lateral root growth in Ginseng. In addition, yeast two-hybrid and subcellular localization experiments showed that PgIAA02 interacted with PgARF22/PgARF36 (ARF: auxin response factor) in the nucleus and participated in the biological process of root development. The above results lay the foundation for an in-depth study of Aux/IAA and provide preliminary information for further research on the role of the Aux/IAA gene family in the root development of Ginseng.

Multi-locus genome-wide association study reveal genomic regions underlying root system architecture traits in Ethiopian sorghum germplasm.

The identification of genomic regions underlying the root system architecture (RSA) is vital for improving crop abiotic stress tolerance. To improve sorghum (Sorghum bicolor L. Moench) for environmental stress tolerance, information on genetic variability and genomic regions linked to RSA traits is paramount. The aim of this study was, therefore, to investigate common quantitative trait nucleotides (QTNs) via multiple methodologies and identify genomic regions linked to RSA traits in a panel of 274 Ethiopian sorghum accessions. Multi-locus genome-wide association study was conducted using 265,944 high-quality single nucleotide polymorphism markers. Considering the QTN detected by at least three different methods, a total of 17 reliable QTNs were found to be significantly associated with root angle, number, length, and dry weight. Four QTNs were detected on chromosome SBI-05, followed by SBI-01 and SBI-02 with three QTNs each. Among the 17 QTNs, 11 are colocated with previously identified root traits quantitative trait loci and the remaining six are genome regions with novel genes. A total of 118 genes are colocated with these up- and down-streams of the QTNs. Moreover, five QTNs were found intragenic. These QTNs are S5_8994835 (number of nodal roots), S10_55702393 (number of nodal roots), S1_56872999 (nodal root angle), S9_1212069 (nodal root angle), and S5_5667192 (root dry weight) intragenic regions of Sobic.005G073101, Sobic.010G198000, Sobic.001G273000, Sobic.009G013600, and Sobic.005G054700, respectively. Particularly, Sobic.005G073101, Sobic.010G198000, and Sobic.009G013600 were found responsible for the plant growth hormone-induced RSA. These genes may regulate root development in the seedling stage. Further analysis on these genes might be important to explore the genetic structure of RSA of sorghum.

The BTB/TAZ domain-containing protein CmBT1-mediated CmANR1 ubiquitination negatively regulates root development in chrysanthemum.

Roots are fundamental for plants to adapt to variable environmental conditions. The development of a robust root system is orchestrated by numerous genetic determinants and, among them, the MADS-box gene ANR1 has garnered substantial attention. Prior research has demonstrated that, in chrysanthemum, CmANR1 positively regulates root system development. Nevertheless, the upstream regulators involved in the CmANR1-mediated regulation of root development remain unidentified. In this study, we successfully identified bric-a-brac, tramtrack and broad (BTB) and transcription adapter putative zinc finger (TAZ) domain protein CmBT1 as the interacting partner of CmANR1 through a yeast-two-hybrid (Y2H) screening library. Furthermore, we validated this physical interaction through bimolecular fluorescence complementation and pull-down assays. Functional assays revealed that CmBT1 exerted a negative influence on root development in chrysanthemum. In both in vitro and in vivo assays, it was evident that CmBT1 mediated the ubiquitination of CmANR1 through the ubiquitin/26S proteasome pathway. This ubiquitination subsequently led to the degradation of the CmANR1 protein and a reduction in the transcription of CmANR1-targeted gene CmPIN2, which was crucial for root development in chrysanthemum. Genetic analysis suggested that CmBT1 modulated root development, at least in part, by regulating the level of CmANR1 protein. Collectively, these findings shed new light on the regulatory role of CmBT1 in degrading CmANR1 through ubiquitination, thereby repressing the expression of its targeted gene and inhibiting root development in chrysanthemum.

The ABA synthesis enzyme allele OsNCED2T promotes dryland adaptation in upland rice

Upland rice shows dryland adaptation in the form of a deeper and denser root system and greater drought resistance than its counterpart, irrigated rice. Our previous study revealed a difference in the frequency of the OsNCED2 gene between upland and irrigated populations. A nonsynonymous mutation (C to T, from irrigated to upland rice) may have led to functional variation fixed by artificial selection, but the exact biological function in dryland adaptation is unclear. In this study, transgenic and association analysis indicated that the domesticated fixed mutation caused functional variation in OsNCED2, increasing ABA levels, root development, and drought tolerance in upland rice under dryland conditions. OsNCED2-overexpressing rice showed increased reactive oxygen species-scavenging abilities and transcription levels of many genes functioning in stress response and development that may regulate root development and drought tolerance. OsNCED2T-NILs showed a denser root system and drought resistance, promoting the yield of rice under dryland conditions. OsNCED2T may confer dryland adaptation in upland rice and may find use in breeding dryland-adapted, water-saving rice.

Comparative Study of Small-RNA and Degradome Sequencing Reveals Role of Novel stu-miR8006 in Regulating Root Development in Solanum tuberosum L.

MicroRNAs are a class of endogenous, non-coding, small-RNA molecules with important functions in plant development and stress response processes. Root systems are important because they allow plants to absorb nutrients and water from the soil and are fundamental for anchoring the plant and responding to environmental signals. However, the roles of miRNAs underlying root development remain poorly investigated in potato. In this research, small-RNA sequencing was performed to thoroughly detect underlying miRNAs and their roles in regulating root development between the early root (ER) stage and the mature root (MR) stage of potato roots. A total of 203 known and 137 novel miRNAs were obtained, and 64 differentially expressed miRNAs (DEMs) were identified between the ER and MR stages. The expression patterns of 12 DEMs were also determined via qRT-PCR. In addition, a mixed degradome library was constructed from the ER and the MR stages to identify the targets of the identified miRNAs, and 2400 target genes were verified to be the targets of 131 miRNAs. Based on target annotation, we identified that nine target genes of six DEMs were probably involved in potato root development, and eight targets of six DEMs were validated via 5’-RLM-RACE assays. These targets may participate in root development by regulating cell proliferation, root cultures (PGSC0003DMT400013837), root meristem growth (PGSC0003DMT400079970), root morphogenesis (PGSC0003DMT400040282), post-embryonic root development (PGSC0003DMT400021612), root hair elongation (PGSC0003DMT400034518), cell wall repair (PGSC0003DMT400074930), and auxin polar transport (PGSC0003DMT400079970), and by negatively regulating cell proliferation (PGSC0003DMT400009997) and cell growth (PGSC0003DMT400003464). The qRT-PCR analysis indicated that most miRNAs have opposing expression patterns to their targets. It is widely accepted that potato root development is regulated by miRNAs, among which stu-miR8006-p5-1ss9AT is substantially down-regulated during root development. We show here that the suppression of stu-miR8006-p5-1ss9AT led to an alteration in the potato root architecture and that it targeted auxin induction in the root culture protein 12-encoding gene that is potentially involved in the regulation of root development. In addition, the suppression of stu-miR8006-p5-1ss9AT led to a significant alteration in the potato root architecture. Altogether, our results might provide some useful insights into stu-miR8006-p5-1ss9AT and the crucial role that it plays in potato root development; they could also facilitate the molecular genetic breeding of potato.

The cold-induced factor CBF3 mediates root stem cell activity, regeneration, and developmental responses to cold

Plant growth and development involve the specification and regeneration of stem cell niches (SCNs). Although plants are exposed to disparate environmental conditions, how environmental cues affect developmental programs and stem cells is not well understood. Root stem cells are accommodated in meristems in SCNs around the quiescent center (QC), which maintains their activity. Using a combination of genetics and confocal microscopy to trace morphological defects and correlate them with changes in gene expression and protein levels, we show that the cold-induced transcription factor (TF) C-REPEAT BINDING FACTOR 3 (CBF3), which has previously been associated with cold acclimation, regulates root development, stem cell activity, and regeneration. CBF3 is integrated into the SHORT-ROOT (SHR) regulatory network, forming a feedback loop that maintains SHR expression. CBF3 is primarily expressed in the root endodermis, whereas the CBF3 protein is localized to other meristematic tissues, including root SCNs. Complementation of cbf3-1 using a wild-type CBF3 gene and a CBF3 fusion with reduced mobility show that CBF3 movement capacity is required for SCN patterning and regulates root growth. Notably, cold induces CBF3, affecting QC activity. Furthermore, exposure to moderate cold around 10°C–12°C promotes root regeneration and QC respecification in a CBF3-dependent manner during the recuperation period. By contrast, CBF3 does not appear to regulate stem cell survival, which has been associated with recuperation from more acute cold (∼4°C). We propose a role for CBF3 in mediating the molecular interrelationships among the cold response, stem cell activity, and development.

Transcriptomic Analysis Reveals the Response Mechanisms of Bell Pepper (Capsicum annuum) to Phosphorus Deficiency.

Phosphorus (P) is an important nutritional element needed by plants. Roots obtain P as inorganic phosphate (Pi), mostly in H2PO-4 form. It is vital for plants to have a sufficient supply of Pi since it participates in important processes like photosynthesis, energy transfer, and protein activation, among others. The physicochemical properties and the organic material usually make Pi bioavailability in soil low, causing crops and undomesticated plants to experience variations in accessibility or even a persistent phosphate limitation. In this study, transcriptome data from pepper roots under low-Pi stress was analyzed in order to identify Pi starvation-responsive genes and their relationship with metabolic pathways and functions. Transcriptome data were obtained from pepper roots with Pi deficiency by RNASeq and analyzed with bioinformatic tools. A total of 97 differentially expressed genes (DEGs) were identified; Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that metabolic pathways, such as porphyrin and chlorophyll metabolism, were down-regulated, and galactose and fatty acid metabolism were up-regulated. The results indicate that bell pepper follows diverse processes related to low Pi tolerance regulation, such as the remobilization of internal Pi, alternative metabolic pathways to generate energy, and regulators of root development.

Mixture of controlled-release and normal urea to improve maize root development, post-silking plant growth, and grain filling

The mixture of controlled-release urea (CRU) and normal urea (MCU) applied as one-time basal fertilizer is a convenient and effective alternative to traditional split-nitrogen (N) fertilization, can ensure a sufficient late-season N supply to increase maize yield. However, the effects of MCU ratios on maize root development, post-silking growth, and grain-filling process remain poorly understood. In this study, 3-year field experiments were conducted on sandy and clay soils in Northeast China, to evaluate maize yield responses to different MCU ratios (from 0% to 60% at 15% intervals). Four key treatments, i.e., N omission (N0), MCU0%, MCU30%, and MCU60%, were then selected to investigate root traits, post-silking plant growth and N uptake, grain-filling parameters, and their relationships with grain yields. Across different soils and years, grain yields showed a parabolic curve with increasing MCU ratios, with the highest yields obtained in MCU30%. On average, MCU30% increased grain yield by 22.3% and 11.7% on sandy and clay soils, respectively, relative to MCU0%. The appropriate early-N supply in MCU30% promoted root growth by allocating more dry matter (DM) to roots, while increasing total root length by producing more and longer crown roots, as well as higher lateral root length. The well-developed roots in MCU30% increased post-silking plant N uptake under sufficient late-N supply, thereby delayed leaf senescence and improved DM production for grain-filling, ultimately increased kernel weight and grain yield. Compared to MCU30%, MCU60% showed similar growth and yield performances on clay soil. In contrast, MCU60% performed notably worse on sandy soil due to limited CRU-N release at early period under inherently lower soil moisture and fertility levels. Our measurements and correlation analysis support the conclusion that MCU30% effectively sustain leaf longevity and increase post-silking DM by optimizing root growth and morphology under an optimal N supply pattern during maize growing season, thus improving grain-filling and final yield. The results advance our understanding of how MCU method affects maize post-silking growth and yield formation, providing important insights for optimizing crop N management by regulating root development, especially on lower fertility soils.

Regulation of root development in nitrogen-susceptible and nitrogen-tolerant sweet potato cultivars under different nitrogen and soil moisture conditions

BackgroundDue to unreasonable nitrogen (N) application and water supply, sweet potato vines tend to grow excessively. Early development of storage roots is conducive to inhibiting vine overgrowth. Hence, we investigated how N and soil moisture affect early root growth and development.ResultsA pot experiment was conducted using the sweet potato cultivars Jishu26 (J26, N-susceptible) and Xushu32 (X32, N-tolerant). Two N application rates of 50 (N1) and 150 mg kg− 1 (N2) and two water regimes, drought stress (DS) (W1) and normal moisture (W2), were applied to each cultivar. For J26, the lowest expansion root weight was observed in the N2W2 treatment, while for X32, the N1W2 and N2W2 treatments resulted in higher root weights compared to other treatments. The interaction between N rates and water regimes significantly affected root surface area and volume in J26. Root cross-sections revealed that N2W2 increased the percentage of root area covered by xylem vessels and decreased the amount of secondary xylem vessels (SXV) in J26. However, in X32, it increased the number of SXV. A high N rate reduced the 13 C distribution ratio in J26 expansion roots, but had no significant effect on X32. In J26, N2W2 inhibited starch synthesis in roots by downregulating the expression of AGPa, AGPb, GBSS I, and SBE I.ConclusionThe observed effects were more pronounced in J26. For X32, relatively high N and moisture levels did not significantly impact storage root development. Therefore, special attention should be paid to N supply and soil moisture for N-susceptible cultivars during the early growth stage.

Spatial transcriptomics of a lycophyte root sheds light on root evolution

Plant roots originated independently in lycophytes and euphyllophytes, whereas early vascular plants were rootless. The organization of the root apical meristem in euphyllophytes is well documented, especially in the model plant Arabidopsis. However, little is known about lycophyte roots and their molecular innovations during evolution. In this study, spatial transcriptomics was used to detect 97 root-related genes in the roots of the lycophyte Selaginella moellendorffii. A high number of genes showed expression patterns similar to what has been reported for seed plants, supporting the idea of a highly convergent evolution of mechanisms to control root development. Interaction and complementation data of SHORTROOT (SHR) and SCARECROW (SCR) homologs, furthermore, support a comparable regulation of the ground tissue (GT) between euphyllophytes and lycophytes. Root cap formation, in contrast, appears to be differently regulated. Several experiments indicated an important role of the WUSCHEL-RELATED HOMEOBOX13 gene SmWOX13a in Selaginella root cap formation. In contrast to multiple Arabidopsis WOX paralogs, SmWOX13a is able to induce root cap cells in Arabidopsis and has functionally conserved homologs in the fern Ceratopteris richardii. Lycophytes and a part of the euphyllophytes, therefore, may share a common mechanism regulating root cap formation, which was diversified or lost during seed plant evolution. In summary, we here provide a new spatial data resource for the Selaginella root, which in general advocates for conserved mechanisms to regulate root development but shows a clear divergence in the control of root cap formation, with a novel putative role of WOX genes in root cap formation in non-seed plants.

Biochar application promotes crops yield through regulating root development and the community structure of root endophytic fungi in wheat-maize rotation

Biochar incorporation into soil has been found to benefit crop yield. However, the effects of biochar application on crop root growth and morphology and root endophytic fungi in different crop growth stages remain obscure. Here, a field experiment was established with various biochar rates [0 (control), 4.5 t ha−1 (BC4.5), 9 t ha−1 (BC9)] to examine the effect of biochar application on root development and community structure of root endophytic fungi in a wheat-maize rotation system under semi-arid climate on alluvial soil. The results showed that in BC9 the total root length of maize and shoot nutrient accumulation in the flowering stage were comparable with the control and BC4.5. However, in the grain-filling stage, the root length remained high in BC9, but it was reduced by 21–34% in the control compared with the flowering period, suggesting biochar delayed root senescence. Similarly, the higher specific root length was found in BC9 compared with the control at the grain-filling stage. Biochar also altered the relative abundance and diversity of root endophytic fungi. Ascomycetes and Basidiomycetes dominated the root fungal community, accounting for 57–85% of the total endophytes. Biochar changed the core species in the community structure from Basidiomycetes to Ascomycetes and promoted shoot nutrient accumulation and final grain yield of wheat and maize. Thus, biochar maybe increases crop yield by increasing root length, delaying root senescence, and altering the community structure of root endophytic fungi.

The drought-responsive factor MdDREB2A affects root development by directly regulating the transcription of MdARF6

Drought is one of the most common abiotic stresses, which affects plant growth and root system architecture. Auxin is a key phytohormone in regulating root structures. However, how drought and auxin jointly regulate root development is still less studied. In this study, it was found that APETALA2/ethylene-responsive element binding factors (AP2/ERF) transcription factor MdDREB2A could affect root development by regulating the transcription of AUXIN RESPONSE FACTOR 6 (MdARF6). Overexpression of MdDREB2A promoted root development both in apple and Arabidopsis. Further assays showed that MdDREB2A could regulate the expression of auxin related genes ARFs/IAAs. In addition, MdDREB2A could directly bind to the DRE cis-element in the promoter of MdARF6 to activate its transcription. Meanwhile, MdDREB2A could also promote the expression of auxin-responsive Gretchen Hagen3s (MdGH3s), which act the downstream of ARF6, thereby further regulating auxin-mediated root development. This work provides a novel perspective for drought and auxin crosstalk to regulate root development.

Comparative transcriptome analysis reveals the regulatory effects of exogenous auxin on lateral root development and tanshinone accumulation in Salvia miltiorrhiza.

The physiological and transcriptome analysis revealed that auxin was a positive regulator of lateral root development and tanshinone accumulation in Salvia miltiorrhiza. Roots of S. miltiorrhiza are widely used as medicinal materials in China, and the root morphology and content of bioactive compounds [such as phenolic acids and diterpenoid quinones (tanshinones)] are the main factors to determine the quality of this herb. Auxin regulates root development and secondary metabolism in many plant species, but little is known about its function in S. miltiorrhiza. In this study, S. miltiorrhiza seedlings were treated (exogenous application) with the auxin indole-3-acetic acid (IAA) and the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) to investigate the regulatory roles of auxin in S. miltiorrhiza. The results indicated that exogenous IAA promoted both lateral root development and tanshinones biosynthesis in S. miltiorrhiza. The NPA application suppressed the lateral root development but showed no obvious effects on tanshinones accumulation. Based on the RNA-seq analysis, expressions of genes related to auxin biosynthesis and signaling transduction were altered in both treated groups. Coincidental with the enhanced content of tanshinones, transcripts of several key enzyme genes in the tanshinones biosynthetic pathway were stimulated after the exogenous IAA application. The expression profiles of seven common transcription factor domain-containing gene families were analyzed, and the results implied that some AP2/ERF genes were probably responsible for the auxin-induced lateral root development in S. miltiorrhiza. These findings shed new light on the regulatory roles of auxin on root development and bioactive compounds biosynthesis in S. miltiorrhiza, and lay the groundwork for future research into the detailed molecular mechanism underlying these biological functions.

Nuclear translocation of OsMADS25 facilitated by OsNAR2.1 in reponse to nitrate signals promotes rice root growth by targeting OsMADS27 and OsARF7

Nitrate is an important nitrogen source and signaling molecule that regulates plant growth and development. Although several components of the nitrate signaling pathway have been identified, the detailed mechanisms are still unclear. Our previous results showed that OsMADS25 can regulate root development in response to nitrate signals, but the mechanism is still unknown. Here, we try to answer two key questions: how does OsMADS25 move from the cytoplasm to the nucleus, and what are the direct target genes activated by OsMADS25 to regulate root growth after it moves to the nucleus in response to nitrate? Our results demonstrated that OsMADS25 moves from the cytoplasm to the nucleus in the presence of nitrate in an OsNAR2.1-dependent manner. Chromatin immunoprecipitation sequencing, chromatin immunoprecipitation qPCR, yeast one-hybrid, and luciferase experiments showed that OsMADS25 directly activates the expression of OsMADS27 and OsARF7, which are reported to be associated with root growth. Finally, OsMADS25-RNAi lines, the Osnar2.1 mutant, and OsMADS25-RNAi Osnar2.1 lines exhibited significantly reduced root growth compared with the wild type in response to nitrate supply, and expression of OsMADS27 and OsARF7 was significantly suppressed in these lines. Collectively, these results reveal a new mechanism by which OsMADS25 interacts with OsNAR2.1. This interaction is required for nuclear accumulation of OsMADS25, which promotes OsMADS27 and OsARF7 expression and root growth in a nitrate-dependent manner.