Published Research

Exploring the role of Proanthocyanidins in plant: A new tool for confocal microscopy 

Figure: We apply biolistic DNA Delivery for Transiently Induced Gene Silencing and Transient Over-Expression to know the function of xylan biosynthesis gene against powdery mildew pathogen. 

Figure: Transient induced gene silencing of candidate genes and the changes in susceptibility to fungal penetration.  


Research article (Collaborative): Differential expression of microRNAs and potential targets under drought stress in barley.

Drought is a crucial environmental constraint limiting crop production in many parts of the world. microRNA (miRNA) based gene regulation has been shown to act in several pathways, including crop response to drought stress. Sequence based profiling and computational analysis have revealed hundreds of miRNAs and their potential targets in different plant species under various stress conditions, but few have been biologically verified. In this study, 11 candidate miRNAs were tested for their expression profiles in barley. Differences in accumulation of only four miRNAs (Ath-miR169b, Osa-miR1432, Hv-miRx5 and Hv-miR166b/c) were observed between drought-treated and well-watered barley in four genotypes. miRNA targets were predicted using degradome analysis of two, different genotypes, and genotype-specific target cleavage was observed. Inverse correlation of mature miRNA accumulation with miRNA target transcripts was also genotype dependent under drought treatment. Drought-responsive miRNAs accumulated predominantly in mesophyll tissues. Our results demonstrate genotype-specific miRNA regulation under drought stress and evidence for their role in mediating expression of target genes for abiotic stress response in barley. 

Note: Although drought stress is not my direct research area of interest, I contributed to this project for microscopic image analysis. 

1 September 2016

Check out the full article published in Plant, Cell and Environment here 

Figure

Light micrographs of the expression of Ath-miR169b and the target transcript encoding NFY-A by in situ PCR in Hindmarsh flag leaf sections from booting stage. Negative controls of miR169b are shown in (a) well-watered and (b) drought treated samples. Negative controls of NFY-A are shown in (c) well-watered and (d) drought-treated samples. miR169b expression is shown in (e) well-watered and (f) drought-treated samples. NFY-A expression is shown in (g) well-watered and (h) drought-treated samples. Magnified view of the red boxed area of respective middle panel is shown the right panel (i–l). The blue stain indicates the presence of transcripts. Scale bar is 100 μm. PH, phloem; XY, xylem; BS, bundle sheath; CO, collenchyma, MS, mesophyll cells.

Review article: The Plant Cell Wall: A Complex and Dynamic Structure As Revealed by the Responses of Genes under Stress Conditions.

The plant cell wall has a diversity of functions. It provides a structural framework to support plant growth and acts as the first line of defense when the plant encounters pathogens. The cell wall must also retain some flexibility, such that when subjected to developmental, biotic, or abiotic stimuli it can be rapidly remodeled in response. Genes encoding enzymes capable of synthesizing or hydrolyzing components of the plant cell wall show differential expression when subjected to different stresses, suggesting they may facilitate stress tolerance through changes in cell wall composition. In this review we summarize recent genetic and transcriptomic data from the literature supporting a role for specific cell wall-related genes in stress responses, in both dicot and monocot systems. These studies highlight that the molecular signatures of cell wall modification are often complex and dynamic, with multiple genes appearing to respond to a given stimulus. Despite this, comparisons between publically available datasets indicate that in many instances cell wall-related genes respond similarly to different pathogens and abiotic stresses, even across the monocot-dicot boundary. We propose that the emerging picture of cell wall remodeling during stress is one that utilizes a common toolkit of cell wall-related genes, multiple modifications to cell wall structure, and a defined set of stress-responsive transcription factors that regulate them.

Note: A review article published in Frontiers in Plant Science as shared co-author. 

Check out here 

Commentary: Cellulose/callose glucan networks: the key to powdery mildew resistance in plants?

A brilliant commentary on our Callose and cellulose synthase paper by Christian Voigt.

‘This opens new opportunities for studying regulatory mechanisms of papilla formation in an important crop species and supports new molecular breeding approaches for increased penetration resistance.’ 

Check out here 

Research article (collaborative): The barley cellulose synthase-like D2 gene (HvCslD2) mediates penetration resistance to host-adapted and nonhost isolates of the powdery mildew fungus. 

Cell walls and cellular turgor pressure shape and suspend the bodies of all vascular plants. In response to attack by fungal and oomycete pathogens, which usually breach their host's cell walls by mechanical force or by secreting lytic enzymes, plants often form local cell wall appositions (papillae) as an important first line of defence. The involvement of cell wall biosynthetic enzymes in the formation of these papillae is still poorly understood, especially in cereal crops.

To investigate the role in plant defence of a candidate gene from barley (Hordeum vulgare) encoding cellulose synthase-like D2 (HvCslD2), we generated transgenic barley plants in which HvCslD2 was silenced through RNA interference (RNAi).

The transgenic plants showed no growth defects but their papillae were more successfully penetrated by host-adapted, virulent as well as avirulent nonhost isolates of the powdery mildew fungus Blumeria graminis. Papilla penetration was associated with lower contents of cellulose in epidermal cell walls and increased digestion by fungal cell wall degrading enzymes.

The results suggest that HvCslD2-mediated cell wall changes in the epidermal layer represent an important defence reaction both for nonhost and for quantitative host resistance against nonadapted wheat and host-adapted barley powdery mildew pathogens, respectively.

1 July 2016

Note: My contribution to the project is as a co-author where I analyze cellulose levels in papillae. 

Figure 2

Silencing of barley (Hordeum vulgare) cellulose synthase-like D2 (HvCslD2) in transgenic plants of barley specifically enhanced disease susceptibility. (a) Reduced nonhost and quantitative host resistance (NHR and QR, respectively) in segregating populations of transgenic T1 plants. Penetration efficiency (PE) of Blumeria graminis f.sp. tritici (Bgt) on the second leaf was determined under the microscope 48 h after inoculation. Transgenic plants expressing green fluorescent protein (GFP) or a GFP-silencing construct were used as additional controls. Infection severity of B. graminis f.sp. hordei (Bgh) was scored macroscopically on the third to fifth leaves 7 d after inoculation and related to average infection values of wild-type plants. The red bars indicate the two selected events HvCslD2_RNAi_E28 (E28) and HvCslD2_RNAi_E39 (E39) used in all subsequent experiments. (b) Silencing of HvCslD2 in leaves of E28 and E39 as shown by RNA-blot hybridization. RNA was isolated from single transgenic plants of E28 or E39, from pools of azygous individuals from the segregating T2 lines used, or from wild-type (wt) plants. Ethidium bromide-stained gel loading and blotting controls are shown below. (c) Normal growth of homozygous T2 plants of E28 and E39, compared with wild-type or GUS-expressing transgenic control plants. (d, e) Normal formation of root hairs by a transgenic plant of E39. (f, g) Nonhost immunity of wild-type plants (f) and abundant hyphal growth on a leaf of a transgenic T2 plant of E28 (g) at 6 d after inoculation.  

Check out the full article published in New phytologist here

Commentary: The effective papilla hypothesis- a commentary on our papilla paper by Ralph Huckelhoven. 

Chowdhury et al. used cell wall probes and antibodies for a beautiful visualization and quantification of cell wall polymers in barley papillae under attack from B. graminis f. sp. hordei.’ 

Check out here

20 October 2014

Fortifying the Fortress: Unlocking the secrets of plant cell wall defense