Abstract
Brassinosteroids (BRs) hormones are important for plant growth, development and immune responses. They are sensed by the transmembrane receptor kinase Brassinosteroid-Insensitive 1 (BRI1) when they bind to its extracellular Leu-rich repeat (LRR) domain. We cloned and characterized the TaBRI1 from T. aestivum and raised overexpression transgenics in Arabidopsis to decipher its functional role. TaBRI1 protein consists of a putative signal peptide followed by 25 leucine rich repeats (LRR), a transmembrane domain and a C-terminal kinase domain. The analysis determined the interaction of TaBRI1 with five members of the wheat Somatic Embryogenesis Receptor Kinase (TaSERKs) gene family (TaSERK1, TaSERK2, TaSERK3, TaSERK4 and TaSERK5), at the plasma membrane. Furthermore, overexpression of TaBRI1 in Arabidopsis leads to the early flowering, increased silique size and seed yield. Root growth analysis of TaBRI1 overexpressing transgenic plants showed hypersensitivity to epi-brassinolide (epi-BL) hormone in a dose-dependent manner. Interestingly, transgenic Arabidopsis plants show thermotolerance phenotype at the seedling stages as revealed by chlorophyll content, photosystem II activity and membrane stability. The transcriptome profiling on the basis of microarray analysis indicates up-regulation of several genes related to brassinosteroid signaling pathway, abiotic stress response, defense response and transcription factors. These studies predict the possible role of TaBRI1 gene in plant growth and development imparting tolerance to thermal stress.
Highlights
Plant growth regulators brassinosteroids (BRs) are ubiquitously present throughout the plant kingdom and play a pivotal role in plant growth and development with regulatory functions during cell elongation, cell division, vascular differentiation, biotic and abiotic stress response and senescence [1, 2]
TaBRI1 protein sequence revealed that its polypeptide (Fig 1a) harbours 25 leucine rich repeat (LRR) from position 199 to 514 amino acid among which eight leucine rich repeats (LRR) domains are highly conserved that are a characteristic feature of BR receptor, PFAM LRR_1 domain from position 633 to 655 amino acid suggested to be involved in diverse protein-protein interactions, followed by a transmembrane region from position 721 to 743 amino acid and a long stretch of kinase _Tyr domain from position 810 to 1083 amino acid comprising of serine/threonine kinase and tyrosine protein kinase at C- terminal end that possibly takes part in most of the cellular activities
We describe here the isolation and characterization of TaBRI1 gene from T. aestivum, most closely related to the H. vulgare, HvBRI1
Summary
Plant growth regulators brassinosteroids (BRs) are ubiquitously present throughout the plant kingdom and play a pivotal role in plant growth and development with regulatory functions during cell elongation, cell division, vascular differentiation, biotic and abiotic stress response and senescence [1, 2]. BRI1 gene was first identified and characterized in Arabidopsis as a BR insensitive mutant [4] In recent years, it was isolated from various plant species, including dicots viz., Pisum sativum [5], Lycopersicon esculentum [6], Gossypium hirsutum [7] and Glycine max [8] and monocots such as Oryza sativa [9] and Hordeum vulgare [10]. In H. vulgare, the BRI1 mutant showed similar BR insensitive mutant phenotype which leads to lodging resistance [10]. All these investigations develops our interest to study the BRI1 function in wheat which is one of the major crop plant
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