Abstract
A dwarf mutant (dwf1) was obtained among 15 transgenic lines, when TaLEA (Tamarix androssowii late embryogenesis abundant gene) was introduced into Populus simonii × Populus nigra by Agrobacterium tumefaciens-mediated transformation. Under the same growth conditions, dwf1 height was significantly reduced compared with the wild type and the other transgenic lines. Because only one transgenic line (dwf1) displayed the dwarf phenotype, we considered that T-DNA insertion sites may play a role in the mutant formation. The mechanisms underlying this effect were investigated using TAIL-PCR (thermal asymmetric interlaced PCR) and microarrays methods. According to the TAIL-PCR results, two flanking sequences located on chromosome IV and VIII respectively, were cloned. The results indicated the integration of two independent T-DNA copies. We searched for the potential genes near to the T-DNA insertions. The nearest gene was a putative poplar AP2 transcription factor (GI: 224073210). Expression analysis showed that AP2 was up-regulated in dwf1 compared with the wild type and the other transgenic lines. According to the microarrays results, a total of 537 genes involved in hydrolase, kinase and transcription factor activities, as well as protein and nucleotide binding, showed significant alterations in gene expression. These genes were expressed in more than 60 metabolic pathways, including starch, sucrose, galactose and glycerolipid metabolism and phenylpropanoids and flavonoid biosyntheses. Our transcriptome and T-DNA insertion sites analyses might provide some useful insights into the dwarf mutant formation.
Highlights
In our previous study, a Tamarix androssowii LEA gene was introduced into Populus simonii × Populus nigra to improve salt tolerance [1]
Our analyses indicated that a putative poplar AP2 transcript factor nearby one T-DNA
To evaluate the potential functions of genes with significant transcriptional changes between the dwf1 mutant and the wild type, gene ontology (GO) categories were assigned to 443 genes of the 537 genes based on the plant GO slim provided by blast2GO [26]
Summary
A Tamarix androssowii LEA gene (lea IV; DQ663481; TaLEA) was introduced into Populus simonii × Populus nigra to improve salt tolerance [1] Among these transgenic lines, only one, dwf, exhibited a dwarf phenotype. Only one, dwf, exhibited a dwarf phenotype This indicated that the T-DNA insertion might be responsible for this mutation. Dwarfism usually results from mutations in genes that regulate the biosyntheses of these plant hormones or are involved in their signaling transduction pathways. Studies on BRASSINOSTEROID-INSENSITIVE1 (BRI1, a receptor of BR) and several other important components involved in BR signaling have provided much insight into many important components in plant development. The T-DNA insertion sits in dwf might be responsible for the dwarf mutant formation, considering that only one transgenic line exhibiting dwarf phenotype. The up-regulated AP2 and the differently expressed genes in dwf might give some useful insights for further analyze the dwarf mechanism, All of these results may prove to be potential candidates for global genetic engineering of development regulation in poplar
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