SHORT-ROOT Stabilizes PHOSPHATE1 to Regulate Phosphate Allocation in Arabidopsis

Coordinated distribution of Pi between roots and shoots is an important process that plants use to maintain Pi homeostasis. SHR (SHORT-ROOT) is well-characterized for its function in root radial patterning1-3. Here, we demonstrate a new role of SHR in controlling phosphate (Pi) allocation from roots to shoots by regulating PHOSPHATE1 (PHO1) in the root differentiation zone. We recovered a weak mutant allele of SHR in Arabidopsis which accumulates much less Pi in the shoot and shows constitutive Pi starvation response (PSR) under Pi-sufficient condition. Besides, Pi starvation suppresses SHR protein accumulation and releases its inhibition on the HD-ZIP Ⅲ transcription factor PHB. PHB accumulates and directly binds the promoter of PHO2 to upregulate its transcription, resulting in PHO1 degradation in the xylem-pole pericycle cells. Our findings reveal a previously unrecognized mechanism of how plants repress Pi translocation from roots to shoots in response to Pi starvation.

SHORT-ROOT paralogs mediate feedforward regulation of D-type cyclin to promote nodule formation in soybean

Nitrogen fixation in soybean takes place in root nodules that arise from de novo cell divisions in the root cortex. Although several early nodulin genes have been identified, the mechanism behind the stimulation of cortical cell division during nodulation has not been fully resolved. Here we provide evidence that two paralogs of soybean SHORT-ROOT (GmSHR) play vital roles in soybean nodulation. Expression of GmSHR4 and GmSHR5 (GmSHR4/5) is induced in cortical cells at the beginning of nodulation, when the first cell divisions occur. The expression level of GmSHR4/5 is positively associated with cortical cell division and nodulation. Knockdown of GmSHR5 inhibits cell division in outer cortical layers during nodulation. Knockdown of both paralogs disrupts the cell division throughout the cortex, resulting in poorly organized nodule primordia with delayed vascular tissue formation. GmSHR4/5 function by enhancing cytokinin signaling and activating early nodulin genes. Interestingly, D-type cyclins act downstream of GmSHR4/5, and GmSHR4/5 form a feedforward loop regulating D-type cyclins. Overexpression of D-type cyclins in soybean roots also enhanced nodulation. Collectively, we conclude that the GmSHR4/5-mediated pathway represents a vital module that triggers cytokinin signaling and activates D-type cyclins during nodulation in soybean.

Efficient Editing of CSLD2 Orthologue by CRISPR/Cas9 Affects Cell Morphogenesis of Root Hair in Spinach

CRISPR/Cas9 is a valuable tool and has been extensively employed to perform gene editing in plants. However, CRISPR/Cas9 has not been successfully used in spinach, an important leafy vegetable crop. Here, we precisely edited Spo23361 and Spo10340, two cellulose synthase-like D (CSLD) genes involved in root hair formation of spinach hairy roots, using CRISPR/Cas9 system. Four mutation types (i.e., replacement, insertion, deletion, and combined mutations) were observed, among which the deletion accounted for the vast majority (about 64.1%). Mutation rate differed largely among different targets. Seven homozygous/bi-allelic and eight heterozygous/chimeric mutated lines of Spo23361 were obtained from 15 independent transgenic hairy root lines. All of the seven homozygous/bi-allelic lines displayed bulking and short root hairs, which exhibited the characteristics of Arabidopsis csld2 mutants. Thirteen heterozygous/chimeric mutated lines, but no homozygous/bi-allelic lines, of Spo10340 were obtained from 15 independent transgenic hairy root lines, all of which showed similar phenotype of root hair with normal hairy roots. The transcriptomic analysis further revealed that multiple gene expressions for cell wall modulation and membrane trafficking were disturbed, which might result in the inhibition of root hair growth in Spo23361 mutants. Our results indicate that Agrobacterium rhizogenes-mediated transformation using CRISPR/Cas9 is a simple and efficient genome editing tool in spinach. It lays a solid foundation for large-scale genome editing in spinach in future.

Association between Smoking during Pregnancy and Short Root Anomaly in Offspring

Short root anomaly (SRA) is a dental anomaly with short dental roots and its pathogenesis is poorly understood. This study investigated the association between maternal smoking during pregnancy and SRA in offspring. A survey was conducted on 558 children aged 8–16 years from two public schools in Ulaanbaatar, Mongolia. SRA was diagnosed using cases with a root-crown ratio of maxillary central incisors of ≤1.0. A questionnaire survey was conducted to assess maternal lifestyle habits. Multiple logistic regression was used to analyse the association between maternal smoking during pregnancy and SRA in offspring after adjusting for possible confounders. The prevalence of SRA in these children was 14.2%. Children whose mothers smoked from pregnancy to date were found to be 4.95 times (95% confidence interval [CI]: 1.65–14.79) more likely to have SRA than those whose mothers never smoked, after adjusting for possible confounders. Additionally, children whose mothers had been exposed to passive smoking during pregnancy were found to be 1.86 times (95% CI: 1.02–3.40) more likely to have SRA than those whose mothers had not been exposed to passive smoke. Our population-based study suggests that maternal and passive smoking exposure during pregnancy can affect tooth root formation in children.

Long-Term Effects of Childhood Cancer Treatment on Dentition and Oral Health: A Dentist Survey Study from the DCCSS LATER 2 Study

Objectives: The aim of this study was to identify the prevalence of and independent risk factors for long-term effects of childhood cancer treatment on the dentition and oral health in childhood cancer survivors (CCSs). Methods: This cross-sectional study is part of the Dutch Childhood Cancer Survivor Study (DCCSS) LATER 2. CCSs were diagnosed with cancer between 1963 and 2001. This study focuses on survey data of 154 CCSs on whom information about their oral health was received from their dentists (71.3%). Descriptive statistics and univariable and multivariable Poisson regression analyses were performed to determine the association between treatment characteristics and oral health data. Results: Of the study group, 36.3% had at least one DDD. The most prevalent DDDs were short-root anomaly (14.6%), agenesis (14.3%), and microdontia (13.6%). Risk factors for at least one DDD were younger age at diagnosis (<3 years) and dose-dependent alkylating agent therapy. Conclusions: This study provides more insight into risk factors for oral health problems in Dutch CCSs. This information is essential in order to improve early detection, prevention, dental care, and quality of life. Further studies are needed in order to better define dose-related radiotherapy exposure of the developing teeth in correlation with oral health problems.

Respon Pertumbuhan Bibit Kakao (Theobroma cacao L.) Terhadap Pemberian Kompos Limbah Kelapa Sawit

Cacao (Theobroma cacao L.) is one of the important plantation commodities after oil palm and rubber. This plant has a high economic value and is a foreign exchange earner. The seeds produced are used as raw material for the foodstuff industry as well as for the pharmaceutical and cosmetic industries. Based on data from the Central Statistics Agency, the productivity of cocoa-farmers in Jambi is still very low, only reaching 585 kg ha-1. This study aims to obtain a dose of oil palm waste compost to support the growth of cocoa seedlings. The experiment was carried out in Pijon Village, Jaluko District, Muaro Jambi Regency from December 2020 to April 2021. This experiment was carried out using a completely randomized design environment. The treatment design used was compost dosage consisting of 4 levels, namely p0 = without giving compost, p1 = 5 tons ha-1 (7.5 grams per 3 kg of media), p2 = 10 tons ha-1 (15 grams per 3 kg of media) and p3 = 15 tons ha-1 (22.5 grams per 3 kg of media). The observed data were tabulated and analyzed with analysis of variance. If the calculated F value has a significant effect, then the DNMRT further test for 95% accuracy is carried out. The results showed that the application of compost 15 tons ha-1 showed an increase the plant height of 63.78%, the stem diameter of 73.68%, the shoot dry weight 30.83%, the total dry weight 95.12%, an the short root ratio 90.37%.

Root Patterning: Tuning SHORT ROOT Function Creates Diversity in Form

Roots have a fundamental role in plant growth and adaptation to different environments. Diversity in root morphology and architecture enables plants to acquire water and nutrients in contrasting substrate conditions, resist biotic and abiotic stress, and develop symbiotic associations. At its most fundamental level, morphology is determined by discrete changes in tissue patterning. Differences in the number and arrangement of the cell layers in the root can change tissue structure, as well as root length and girth, affecting important productivity traits. Therefore, understanding the molecular mechanisms controlling variation in developmental patterning is an important goal in biology. The ground tissue (GT) system is an ideal model to study the genetic basis of morphological diversity because it displays great interspecific variability in cell layer number. In addition, the genetic circuit controlling GT patterning in Arabidopsis thaliana has been well described, although little is known about species with more complex root anatomies. In this review, we will describe the Arabidopsis model for root radial patterning and present recent progress in elucidating the genetic circuitry controlling GT patterning in monocots and the legume Medicago truncatula (Mt), species that develop roots with more complex anatomies and multilayered cortex.

AtRBOHC/RHD2 vesicular delivery to the apical plasma membrane domain during root hair development

Arabidopsis root hairs develop as long tubular extensions from the rootward pole of trichoblasts and exert polarized tip growth. The establishment and maintenance of root hair polarity is a complex process involving the local apical production of reactive oxygen species (ROS) generated by NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG PROTEIN C/ROOT HAIR DEFECTIVE 2 (AtRBOHC/RHD2). It has been shown that loss-of-function rhd2 mutants have short root hairs that are unable to elongate by tip growth, and this phenotype was fully complemented by GFP-RHD2 expressed under the RHD2 promoter. However, the spatiotemporal mechanism of AtRBOHC/RHD2 subcellular redistribution and delivery to the plasma membrane (PM) during root hair initiation and tip growth are still unclear. Here, we used advanced microscopy for detailed qualitative and quantitative analysis of vesicular compartments containing GFP-RHD2 and characterization of their movements in developing bulges and growing root hairs. These compartments, identified by an independent marker such as the trans-Golgi network (TGN), deliver GFP-RHD2 to the apical PM domain, the extent of which correlates with the stage of root hair formation. Movements of TGN/early endosomes, but not late endosomes, were affected in the bulging domains of the rhd2-1 mutant. Finally, we reveal that accumulation in the growing tip, docking, and incorporation of TGN compartments containing GFP-RHD2 to the apical PM of root hairs requires structural sterols. These results help clarify the mechanism of polarized AtRBOHC/RHD2 targeting, maintenance, and recycling at the apical PM domain, coordinated with different developmental stages of root hair initiation and growth.One-sentence summaryAdvanced microscopy and quantitative analysis of vesicular TGN compartments revealed that delivering GFP-RHD2 to the apical plasma membrane domains of developing bulges and growing root hairs requires structural sterols.

Epithelial Bone Morphogenic Protein 2 and 4 Are Indispensable for Tooth Development

The Bmp2 and Bmp4 expressed in root mesenchyme were essential for the patterning and cellular differentiation of tooth root. The role of the epithelium-derived Bmps in tooth root development, however, had not been reported. In this study, we found that the double abrogation of Bmp2 and Bmp4 from mouse epithelium caused short root anomaly (SRA). The K14-cre;Bmp2f/f;Bmp4f/f mice exhibited a persistent Hertwig’s Epithelial Root Sheath (HERS) with the reduced cell death, and the down-regulated BMP-Smad4 and Erk signaling pathways. Moreover, the Shh expression in the HERS, the Shh-Gli1 signaling, and Nfic expression in the root mesenchyme of the K14-cre;Bmp2f/f;Bmp4f/f mice were also decreased, indicating a disrupted epithelium- mesenchyme interaction between HERS and root mesenchyme. Such disruption suppressed the Osx and Dspp expression in the root mesenchyme, indicating an impairment on the differentiation and maturation of root odontoblasts. The impaired differentiation and maturation of root odontoblasts could be rescued partially by transgenic Dspp. Therefore, although required in a low dosage and with a functional redundancy, the epithelial Bmp2 and Bmp4 were indispensable for the HERS degeneration, as well as the differentiation and maturation of root mesenchyme.

Short Root Anomaly in a Hispanic Population: Risk for Orthodontic Root Resorption

While the presentation of Short Root Anomaly (SRA) in Hispanic patients has been described previously, it is not known if this population is predisposed to increased orthodontic root resorption. This study evaluates the response of pre-existing short roots in Hispanic SRA patients to orthodontic treatment. Selected maxillary and mandibular teeth of 40 Hispanic SRA patients (19 male, 21 female) and 40 age and gender matched Caucasian patients (19 male, 21 female) with normal root length were evaluated for root resorption following comprehensive orthodontic treatment. The age range of the subjects was between 10 and 19 years. Relative root length was calculated before and after orthodontic treatment from digital panoramic radiographs. Overall, statistically significant root resorption occurred in the control group, but orthodontic root resorption was not significant in the Hispanic group (p > 0.05). When genders were separated, Hispanic females did experience a mild degree of root resorption in the upper incisors while resorption in Hispanic males was not significant. Caucasian females experienced greater root resorption than Caucasian males. Hispanic SRA patients may be safely treated with comprehensive orthodontics and could be at no more risk of root resorption than Caucasian patients with normal initial root length.