Biology subjects

Chandran, D.

Publications and source records attributed to Chandran, D..

4 recordsLinked to original sources

bioRxiv2026

An extended N-terminus restrains the plant cell death-inducing ability of the catalytically competent ribonuclease domain in a pea powdery mildew RALPH effector

RALPH (RNase-like proteins associated with haustoria) effectors, which are preferentially expressed in haustoria and structurally resemble fungal T1/F1 RNases, constitute one of the largest effector families in powdery mildew (PM) fungi, yet their functions in dicot-adapted PM species remain poorly understood. Unlike cereal PM RALPHs, which lack the catalytic residues required for RNase activity, some dicot PM RALPHs retain these residues. Here, we performed a comprehensive structural and expression-based characterization of the pea PM Erysiphe pisi RALPH (EpRALPH) repertoire and functionally characterized EpRALPH11, a RALPH effector with partial conservation of the catalytic residues of T1/F1 fungal RNases. Comparative analyses identified multi-RNase-domain RALPHs as a conserved feature of the Erysiphe lineage, while expression profiling showed that many EpRALPHs are preferentially expressed in haustoria during early host colonization. AlphaFold 3-based structural analyses revealed a conserved T1/F1 RNase-like fold despite substantial sequence and surface charge divergence, indicating functional diversification among EpRALPHs. EpRALPH11 enhanced susceptibility to E. pisi in Medicago truncatula, localized to the nucleolus, and induced nucleolar fragmentation when heterologously expressed in Nicotiana benthamiana leaves. Its RNase domain exhibited T1 RNase activity in vitro, supporting the retention of a catalytically competent RNase domain and, together with its nucleolar localization, suggesting that EpRALPH11 targets plant rRNA and disrupts nucleolar functions. The RNase domain induced cell death in N. benthamiana, whereas the full-length protein and catalytic mutants did not. Cell death induction required exclusive nucleolar localization of the RNase domain, and an extended N-terminal intrinsically disordered region suppressed this activity in the full-length protein. Together, our findings reveal a previously unrecognized mechanis regulating RNase activity in a dicot PM RALPH effector and provide new insights into the functional diversification of RALPHs and their adaptation to obligate biotrophy.

plant biology↗

bioRxiv2026

Effector dsRNA delivery via MgFe-layered double hydroxide nanocarriers confers prolonged protection against powdery mildew in pea

Layered double hydroxides (LDHs) have emerged as promising nanocarriers for RNA interference (RNAi)-based crop protection due to their ability to stabilize and effectively deliver pathogen-specific double-stranded RNA (dsRNA). However, their potential against obligate biotrophic pathogens like powdery mildews remains unexplored. In this study, we investigated Magnesium Iron-LDH (MgFe-LDH) nanomaterials as carriers of fungal effector dsRNA (Ef-dsRNA) and evaluated the efficacy of the resulting complex in suppressing Erysiphe pisi (powdery mildew) infection in pea (Pisum sativum) via foliar spray application. The synthesized LDH nanomaterial exhibits strong leaf adherence, biocompatibility, and high dsRNA loading capacity, protects the dsRNA against RNase-mediated degradation, and facilitates its sustained release over time. Foliar spray application of the Ef-dsRNA-LDH complex on intact pea plants results in enhanced gene silencing of the target fungal effector and confers greater and prolonged local and systemic powdery mildew disease protection compared to treatments with dsRNA or LDH alone. Following spray application, the LDH nanomaterial is rapidly taken up by intact pea leaf cells and from the plant into E. pisi hyphae via haustoria, enabling efficient dsRNA delivery and silencing of the target gene up to 15 days post-application. Overall, our Ef-dsRNA-LDH formulation offers a robust, sustainable, and targeted approach for RNAi-mediated control of powdery mildews.

plant biology↗

bioRxiv2021

Development of a rapid LC-MS/MS method for the simultaneous quantification of various flavonoids and phytohormones extracted from Medicago Truncatula leaves

Flavonoids are small metabolites of plants, which are involved in the regulation of plant development as well as defence against pathogens. Quantitation of these flavonoids in plant samples is highly important and essential in the food and herbal industry. Hence, robust, reliable and sensitive methods are required for the analysis of these compounds in plant samples. In the present study, a high performance liquid chromatographic-tandem mass spectrometric (HPLC- ESI-MS/MS) method was developed and validated for the determination of nine flavonoids, including Liquiritigenin, Naringenin, Genistein, Daidzein, Formononetin, Biochanin A, 2-hydroxy formononetin, 2-methoxyformononetin, Medicarpin, and two phytohormones, Salicylic acid and Jasmonic acid, in Medicago truncatula. The analytes were separated by means of C-18, reversed-phase chromatography and detected using QTRAP mass spectrometer. Molecules were quantified using different transitions in positive and negative ion modes simultaneously in 12 minutes. The on-column limit of detection of all the analytes was as low as 0.03 pg, whereas the limit of quantification of all the compounds was observed upto 0.1 pg levels. Further the method was also validated in terms of specificity, linearity (r2> 0.99), average recovery (90.6 - 110.3%), accuracy (RE% [≤] 3%) and precision (RSD% [≤] 3%). As a proof of concept, the developed method was successfully used for the quantitation of these flavonoids and phytohormones from leaf extract of Medicago truncatula.

biochemistry↗

bioRxiv2020

Genome-Wide High Resolution Expression Map and Functions of Key Cell Fate Determinants Reveal the Dynamics of Crown Root Development in Rice

Shoot borne adventitious/crown roots (AR/CR) shape up the root architecture in grasses. Mechanisms underlying initiation and subsequent outgrowth of CR remain largely unknown. Here, we provide genome-wide modulation in the landscape of transcriptional signatures during distinct developmental stages of CR formation in highly derived grass species, rice. Our studies implicate the role of potential epigenetic modifiers, transcription factors and cell division regulators in priming the initiation of CR primordia followed by progressive activation of conserved transcription regulatory modules to ensure their outgrowth. In depth analysis of spatio-temporal expression patterns of key cell fate determinants and functional analyses of rice WUSCHEL RELATED HOMEOBOX10 (OsWOX10) and PLETHORA (OsPLT1) genes reveal their unprecedented role in controlling root architecture. We further show that OsPLT1 activates local auxin biosynthesis and forms an integral part of ERF3-OsWOX11-OsRR2 regulatory module during CR primordia development. Interestingly, OsPLT genes, when expressed in the transcriptional domain of root-borne lateral root primordia of Arabidopsis plt mutant, rescued their outgrowth demonstrating the conserved role of PLT genes in root primordia outgrowth irrespective of their developmental origin. Together, these findings unveil the molecular framework of cellular reprogramming during trans-differentiation of shoot tissue to root leading to culmination of robust root architecture in grass species which got evolutionary diverged from dicots.

plant biology↗