Isolation and characterization of BnMKK1 responsive to multiple stresses and affecting plant architecture in tobacco

• Published in: Acta physiologiae plantarum 2014-06, Vol.36 (6), p.1313-1324
• Main Authors: Yu, Shunwu, Zhang, Lida, Chen, Chen, Li, Jiajia, Ye, Shuifeng, Liu, Guolan, Mei, Xiaohan, Tang, Kexuan, Luo, Lijun
• Format: Article
• Language: English
• Subjects: abscisic acid; Agriculture; Biomedical and Life Sciences; Brassica napus; complementary DNA; developmental stages; ferns and fern allies; flowers; gene overexpression; genes; hydrogen peroxide; indole acetic acid; leaves; Life Sciences; methyl jasmonate; mitogen-activated protein kinase; mosses and liverworts; open reading frames; Original Paper; Plant Anatomy/Development; plant architecture; Plant Biochemistry; Plant Genetics and Genomics; plant growth; Plant Pathology; Plant Physiology; plant stress; reverse transcriptase polymerase chain reaction; salicylic acid; sodium chloride; Southern blotting; tobacco; water stress
• ISSN: 0137-5881; 1861-1664
• DOI: 10.1007/s11738-014-1510-3

The mitogen-activated protein kinase kinases (MKK) represent a small gene family that is located at the center of the MAPK cascade and play an important role in responses to biotic and abiotic stresses and in plant growth and development. Here, we report the cloning of an MKK gene from Brassica napus, BnMKK1 (GenBank Accession No. HQ916282), by RT-PCR. The BnMKK1 cDNA is 1,447 bp in length with an open reading frame of 1,092 bp. The gene encodes a putative MKK protein that contains a conserved motif S/TxxxxxS/T (where x represents any amino acid) and a MPK docking domain in its N-terminal extension. The orthologues of the BnMKK1 protein are highly conserved among mosses, ferns, dicotyledons and monocotyledons. Southern hybridization revealed the presence of more than two copies of the BnMKK1 homologues in the genome of B. napus. Quantitative reverse transcription–polymerase chain reaction analyses showed that the BnMKK1 transcripts accumulated in response to cold, ABA (abscisic acid) and MeJA (methyl jasmonate) but declined in response to mannitol, NaCl, H₂O₂, and SA (salicylic acid). The inhibitors of MAPK activation, PD98059 and U0126, did not inhibit BnMKK1 transcription. BnMKK1 transgenic tobacco plants grew slower and showed significantly delayed flower times compared to the wild type. Their root development was insensitive to treatment with 100 mM IAA (indole-3-acetic acid). The detached leaves from the transgenic BnMKK1 tobacco plants strengthened the inhibition to bacterial development at later growth stages. The overexpression of BnMKK1 leads to rapid water loss and enhanced sensitivities to drought stress in transgenic tobacco plants. These results show that BnMKK1 plays an important role in the response of plants to pathogenic bacteria and drought stress.