Mutant analyses have revealed that root-type-specific genetic regulators intrinsically determine the maize root system architecture.
Mutant analyses have identified genes regulating shoot-borne root initiation (RTCS) and root hair elongation (RTH1 and RTH3).
CPK10-overexpression and T-DNA insertion mutant analyses have shown that CPK10 is involved in drought stress tolerance.
This is in contrast to IXB, where mutant analyses have identified specific cellulose synthase (CesA) complexes (CesA3 and CesA6) from the plasma membrane as toxin targets [ 8, 9].
Besides, mutant analyses have also revealed that the conserved histone chaperone ASF1 is required for cell proliferation during development in Arabidopsis [ 19].
Furthermore, mutant analyses have demonstrated that Nodal signalling is required for nkx2.5 signalling and, in a similar manner to the scenario in swirl/bmp2b mutants, nkx2.5 expression in Nodal mutants can be restored by ectopic expression of gata5.
However, in contrast to yeast, plants possess multiple histone chaperones in most of the families and mutant analyses have shown that cellular function of the members of some of the families is redundant [ 19, 35, 41].
Double mutant analyses have shown that GUN1 and GUN2– GUN5 define two distinct, but partially redundant signalling pathways that regulate overlapping groups of nuclear genes (Mochizuki et al, 2001; Strand et al, 2003).
Based on the characteristics of the mammalian Gli2 protein, this may not seem so surprising; in contrast to Gli3, Gli2 is inefficiently processed to its repressor form and in line with this, mutant analyses have shown that Gli2 also functions principally as an activator (Ding et al., 1998; Matise et al., 1998).
Genetic mutant screening by direct metabolite analyses has been used successfully to study numerous biochemical pathways in organisms ranging from bacteria to yeast and to higher plants [ 7].
