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Ramaiah M.,Purdue University | Jain A.,National Research Center on Plant Biotechnology | Raghothama K.G.,Purdue University
Plant Physiology

Inorganic phosphate (Pi) availability is a major factor determining growth and consequently the productivity of crops. However, it is one of the least available macronutrients due to its high fixation in the rhizospheres. To overcome this constraint, plants have developed adaptive responses to better acquire, utilize, and recycle Pi. Molecular determinants of these adaptive mechanisms include transcription factors (TFs) that play a major role in transcriptional control, thereby regulating genome-scale networks. In this study, we have characterized the biological role of Arabidopsis thaliana Ethylene Response Factor070 (AtERF070), a Pi starvationinduced TF belonging to the APETALA2/ETHYLENE RESPONSE FACTOR family of TFs in Arabidopsis (Arabidopsis thaliana). It is localized to the nucleus and induced specifically in Pi-deprived roots and shoots. RNA interference-mediated suppression of AtERF070 led to augmented lateral root development resulting in higher Pi accumulation, whereas there were reductions in both primary root length and lateral root number in 12-d-old transgenic seedlings overexpressing AtERF070. When the overexpressing lines were grown to maturity under greenhouse conditions, they revealed a stunted bushy appearance that could be rescued by gibberellic acid application. Furthermore, a number of Pi starvation-responsive genes were modulated in AtERF070-overexpressing and RNA interference lines, thereby suggesting a potential role for this TF in maintaining Pi homeostasis. © 2014 American Society of Plant Biologists. All rights reserved. Source

Chakraborty K.,Indian Agriculture Research Institute | Sairam R.K.,Indian Agriculture Research Institute | Bhattacharya R.C.,National Research Center on Plant Biotechnology
Plant Physiology and Biochemistry

The objective of the present study was to examine the role of SOS pathway in salinity stress tolerance in Brassica spp. An experiment was conducted in pot culture with 4 Brassica genotypes, i.e., CS 52 and CS 54, Varuna and T 9 subjected to two levels of salinity treatments along with a control, viz., 1.65 (S 0), 4.50 (S 1) and 6.76 (S 2) dS m -1. Salinity treatment significantly decreased relative water content (RWC), membrane stability index (MSI) and chlorophyll (Chl) content in leaves and potassium (K) content in leaf, stem and root of all the genotypes. The decline in RWC, MSI, Chl and K content was significantly less in CS 52 and CS 54 as compared to Varuna and T 9. In contrast, the sodium (Na) content increased under salinity stress in all the plant parts in all the genotypes, however, the increase was less in CS 52 and CS 54, which also showed higher K/Na ratio, and thus more favourable cellular environment. Gene expression studies revealed the existence of a more efficient salt overly sensitive pathway composed of SOS1, SOS2, SOS3 and vacuolar Na +/H + antiporter in CS 52 and CS 54 compared to Varuna and T 9. Sequence analyses of partial cDNAs showed the conserved nature of these genes, and their intra and intergenic relatedness. It is thus concluded that existence of an efficient SOS pathway, resulting in higher K/Na ratio, could be one of the major factor determining salinity stress tolerance of Brassica juncea genotypes CS 52 and CS 54. © 2011 Elsevier Masson SAS. Source

Ramaiah M.,Purdue University | Jain A.,Purdue University | Jain A.,National Research Center on Plant Biotechnology | Baldwin J.C.,Purdue University | And 2 more authors.
Plant Physiology

Phosphate (Pi) deficiency is one of the leading causes of loss in crop productivity. Plants respond to Pi deficiency by increasing Pi acquisition and remobilization involving organic and inorganic Pi transporters. Here, we report the functional characterization of a putative organic Pi transporter, Glycerol-3-phosphate permease (G3Pp) family, comprising five members (AtG3Pp1 to -5) in Arabidopsis (Arabidopsis thaliana). AtG3Pp1 and AtG3Pp2 showed 24-and 3-fold induction, respectively, in the roots of Pi-deprived seedlings, whereas Pi deficiency-mediated induction of AtG3Pp3 and -4 was evident in both roots and shoots. Furthermore, promoter-b-glucuronidase (GUS) fusion transgenics were generated for AtG3Pp2 to -5 for elucidation of their in planta role in Pi homeostasis. During Pi starvation, there was a strong expression of the reporter gene driven by AtG3Pp4 promoter in the roots, shoots, anthers, and siliques, whereas GUS expression was specific either to the roots (AtG3Pp3) or to stamens and siliques (AtG3Pp5) in other promoter-GUS fusion transgenics. Quantification of reporter gene activities further substantiated differential responses of AtG3Pp family members to Pi deprivation. A distinct pattern of reporter gene expression exhibited by AtG3Pp3 and AtG3Pp5 during early stages of germination also substantiated their potential roles during seedling ontogeny. Furthermore, an AtG3Pp4 knockdown mutant exhibited accentuated total lateral root lengths under +phosphorus and 2phosphorus conditions compared with the wild type. Several Pi starvation-induced genes involved in root development and/or Pi homeostasis were up-regulated in the mutant. A 9-fold induction of AtG3Pp3 in the mutant provided some evidence for a lack of functional redundancy in the gene family. These results thus reflect differential roles of members of the G3Pp family in the maintenance of Pi homeostasis. © 2011 American Society of Plant Biologists. All Rights Reserved. Source

Jain A.,National Research Center on Plant Biotechnology | Nagarajan V.K.,Purdue University | Raghothama K.G.,Purdue University
Cellular and Molecular Life Sciences

Phosphorus (P), an essential macronutrient required for plant growth and development, is often limiting in natural and agro-climatic environments. To cope with heterogeneous or low phosphate (Pi) availability, plants have evolved an array of adaptive responses facilitating optimal acquisition and distribution of Pi. The root system plays a pivotal role in Pi-deficiency-mediated adaptive responses that are regulated by a complex interplay of systemic and local Pi sensing. Cross-talk with sugar, phytohormones, and other nutrient signaling pathways further highlight the intricacies involved in maintaining Pi homeostasis. Transcriptional regulation of Pi-starvation responses is particularly intriguing and involves a host of transcription factors (TFs). Although PHR1 of Arabidopsis is an extensively studied MYB TF regulating subset of Pistarvation responses, it is not induced during Pi deprivation. Genome-wide analyses of Arabidopsis have shown that low Pi stress triggers spatiotemporal expression of several genes encoding different TFs. Functional characterization of some of these TFs reveals their diverse roles in regulating root system architecture, and acquisition and utilization of Pi. Some of the TFs are also involved in phytohormone-mediated root responses to Pi starvation. The biological roles of these TFs in transcriptional regulation of Pi homeostasis in model plants Arabidopsis thaliana and Oryza sativa are presented in this review. © Springer Basel AG 2012. Source

Chakraborty A.,ICAR Central Research Institute for Jute and Allied Fibres CRIJAF | Sarkar D.,ICAR Central Research Institute for Jute and Allied Fibres CRIJAF | Satya P.,ICAR Central Research Institute for Jute and Allied Fibres CRIJAF | Karmakar P.G.,ICAR Central Research Institute for Jute and Allied Fibres CRIJAF | Singh N.K.,National Research Center on Plant Biotechnology
Molecular Genetics and Genomics

We generated the bast transcriptomes of a deficient lignified phloem fibre mutant and its wild-type jute (Corchorus capsularis) using Illumina paired-end sequencing. A total of 34,163 wild-type and 29,463 mutant unigenes, with average lengths of 1442 and 1136  bp, respectively, were assembled de novo, ~77–79 % of which were functionally annotated. These annotated unigenes were assigned to COG (~37–40 %) and GO (~22–28 %) classifications and mapped to 189 KEGG pathways (~19–21 %). We discovered 38 and 43 isoforms of 16 and 10 genes of the upstream shikimate-aromatic amino acid and downstream monolignol biosynthetic pathways, respectively, rendered their sequence similarities, confirmed the identities of 22 of these candidate gene families by phylogenetic analyses and reconstructed the pathway leading to lignin biosynthesis in jute fibres. We also identified major genes and bast-related transcription factors involved in secondary cell wall (SCW) formation. The quantitative RT-PCRs revealed that phenylalanine ammonia-lyase 1 (CcPAL1) was co-down-regulated with several genes of the upstream shikimate pathway in mutant bast tissues at an early growth stage, although its expression relapsed to the normal level at the later growth stage. However, cinnamyl alcohol dehydrogenase 7 (CcCAD7) was strongly down-regulated in mutant bast tissues irrespective of growth stages. CcCAD7 disruption at an early growth stage was accompanied by co-up-regulation of SCW-specific genes cellulose synthase A7 (CcCesA7) and fasciclin-like arabinogalactan 6 (CcFLA6), which was predicted to be involved in coordinating the S-layers’ deposition in the xylan-type jute fibres. Our results identified CAD as a promising target for developing low-lignin jute fibres using genomics-assisted molecular approaches. © 2015, Springer-Verlag Berlin Heidelberg. Source

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