Triple Mutant Combinations Research Articles

Multiple mutations in the T region of the Agrobacterium tumefaciens tumor-inducing plasmid.

Three genetic loci affecting tumor morphology lie within pTiA6NC T-DNA: tms, tmr, and tml. Using deletions and multiple transposon insertions, we constructed tumor-inducing (Ti) plasmids representing every possible double and triple mutant combination. tms tmr and tms tmr tml mutants did not incite tumors on most plants and produced a very weak response on a few other hosts but tms tml and tmr tml mutants were virulent. Thus, either tms+ or tmr+ alone can promote significant tumor growth but tml+ by itself is not sufficient. On hosts where tms mutants induce tumors accompanied by shoot proliferation, addition of a tml mutation reduces or eliminates shoot proliferation, suggesting that tml+ promotes shoot development. The small calli incited by tms tmr and tms tmr tml mutants contain agropine, an indication that these plant cells incorporate T-DNA in the absence of substantial tumor growth.

Comparative susceptibility of starch granules of double- and triple-mutants containing Amylose-extender, waxy, sugary-1, sugary-2 and dull genes of maize inbred OH43 (Zea mays L.) to amylase.

Starch granules were prepared from 14 double- and 26 triple-mutants containing amylose-extender (ae), 14 double- and 18 triple-mutants containing waxy (wx), 15 double- and 20 triple-mutants containing sugary-1 (su1), 13 double- and 23 triple-mutants containing sugary-2 (su2), and 14 double- and 19 triple-mutants containing dull (du) of maize inbred Oh43 (Zea mays L.). The relative susceptibilities of these starch granules to fungal glucoamylase were determined and the starch granules were examined by scanning electron microscopy. A commercial normal maize starch was used as a control. Starch granules of the double- and triple-mutants containing su1 and su2 were digested two to eight times faster than normal. The ae gene reduced susceptibility and seems to be epistatic to su1 and su2. Starch granules of the double- and triple-mutants containing wx were digested about two times faster than normal and those containing shrunken-2 (sh2) were digested 1.2 to eight times faster than normal. Starch granules of triple-mutant combinations with opaque-2 (o2) showed digestion properties which were comparable to those of their respective monopaque double-mutant counterpart.