Indole-3-acetic acid reverses the harpin-induced hypersensitive response and alters the expression of hypersensitive-response-related genes in tobacco.

Harpin proteins stimulate hypersensitive response (HR) in plants. However, the mechanism by which HR is regulated is not clear. The role of the auxin, indole-3-acetic acid (IAA), in the control of harpin-stimulated HR was investigated. IAA was used to inhibit HR that was stimulated by purified fusion harpin(Xoo) protein in tobacco. Semi-quantitative PCR and qRT-PCR were employed to detect the expression of HR related genes. IAA at 100 µM reversed harpin-induced HR which was inhibited by 500 µM 2,3,5-triiodobenzoic acid (TIBA). Semi-quantitative PCR and qRT-PCR showed the combined application of 100 µM IAA and harpin protein from Xanthomonas oryzae enhanced the expression of HR marker gene, hsr203J, but weakened the expression of the disease-defense gene, chia5. TIBA also decreased the expression of hsr203J but increased the expression of chia5. Thus, the auxin can reverse harpin(Xoo)-induced HR.

[Spotting the positions of T-DNA on the genome for Magnaporthe grisea transformants and study on the mode of T-DNA insertion].

Using thermal asymmetric interlaced PCR (TAIL-PCR), 39 specifical fragments of Magnaporthe grisea genomic DNA flanked on the T-DNA were successfully amplified from 37 M. grisea transformants randomly selected from the mutants induced by T-DNA insertion in our laboratory. These fragments were sequenced and then compared by BLAST with the sequences of M. grisea genomic DNA published in netwwork. T-DNA insertion positions for 17 transformants were spotted on the genome of M. grisea. Of all the 39 amplified specifical fragments, 19 were M. grisea genomic DNA and 20 contained the vector backbone sequences. Of the 19 M. grisea genomic DNA fragments, 10 flanked on the right and 9 on the left border of T-DNA inserted. Of the 10 M. grisea genomic DNA fragments flanked on the right border of T-DNA, 9 had a 102bp identical sequence. However, the 7 fragments flanked on the left border of T-DNA did not have this regularity. The above results demonstrated that T-DNA right nick positions were relatively fixed on the M. grisea genomic DNA, similar to the ones on plant genomic DNA. The spotted positions of T-DNA on the genome for 17 M. grisea transformants established a solid foundation for further functional genomic research of M. grisea.

[Cloning of -tubulin gene and their correlation with conferred carbendazim resistance of Colletotrichum gloeosporioides Penz in mango].

The total DNA isolated from MBC-resistant and MBC-sensitive isolates of Colletotrichum gloeosporioides Penz (C.g.M) of mango were used as templates in PCR amplification using consensus oligo nucleotide primers designed according to the known sequence data of beta-tubulin-encoding gene (tub 1 and tub2) of Colletotrichum gloeosporioides f. sp. aeschynomene (C. g. A). Only the primers designed according to C. g. A tub2 amplified specific fragments. These amplified fragments were cloned and sequenced. The results showed that these fragments have 1344bp and deduced 447 amino acid, which were highly homologous to C.g.A tub2. MBC-resistant isolates did not carry the allelic mutation at amino acid codes 198 and 200 of beta-tubulin gene in comparison with the sensitive isolates. However, the amino acid altered in codes 181, 237 and 363.