Comparison of wild-type and cell death mutant of barley plants containing Mla6 powdery mildew resistance gene

Time-course expression profiles of Bgh challenged barley cultivar C.I. 16151 (harboring the Mla6 powdery mildew resistance allele) and its fast-neutron-derived "Bgh-induced tip cell death1" mutant, bcd1, were compared using the 22K Barley1 GeneChip. Planting, stage of seedlings, harvesting, and experimental design were part of a larger experiment described by Caldo et al. (2004). PLEXdb BB4. Experiment Design: C.I. 16151 (wildtype) and bcd1 (mutant) were planted in separate 20 x 30-cm flats using sterilized potting soil. Each experimental flat consisted of six rows of 15 seedlings, with rows randomly assigned to one of six harvest time points (0, 8, 16, 20, 24, and 32 hai). Seedlings grown to the 1st leaf stage with 2nd leaf unfolded were inoculated with a high density of fresh conidiospores (84 +/- 19 spores/mm2). Groups of flats were placed at 18C (8-hour darkness, 16-hour light) in separate controlled growth chambers corresponding to the Bgh isolates. Rows of plants were harvested at each assigned time points and snap frozen in liquid nitrogen. The entire experiment was repeated three times in a standard split-split-plot design with 72 experimental units (2 genotypes x 2 pathogen isolates x 6 time points x 3 replications). Treatment Description: The samples constituted pairwise combinations of the the cultivar C.I. 16151(containing the Mla6 resistance allele), and its fast-neutron-derived "Bgh-induced tip cell death1" mutant, bcd1 with the two Bgh (Blumeria graminis f. sp. hordei) isolates, 5874 (AvrMla6, AvrMla1) and K1 (AvrMla13, AvrMla1). For each replication, individual genotypes were planted in separate 20 x 30 cm flats using sterilized potting soil. Each experimental flat consisted of six rows of 15 seedlings, with rows randomly assigned to one of six harvest times (0, 8, 16, 20, 24, and 32 hai). Seedlings were grown to the 2nd-leaf stage with 1st leaf unfolded, and inoculation was performed at 4 PM Central Standard Time by tipping the flats at 45oC and dusting the plants with a high density of fresh conidiospores [84 +/- 19 spores/mm2]. This procedure was repeated from the opposite angle to ensure that a high proportion of the cells are in contact with the fungus. This conidial density per unit leaf area routinely results in greater than 50% of epidermal cells that are successfully infected. Groups of flats were placed at 18oC (8 hours darkness, 16 hours light, 8 hours darkness) in separate controlled growth chambers corresponding to the Bgh isolate. Rows of plants were harvested at their assigned harvest times and flash-frozen in liquid nitrogen. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Roger P Wise. The equivalent experiment is BB46 at PLEXdb.]

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Caldo RA, Nettleton D, Wise RP