Petunia hybrida CAROTENOID CLEAVAGE DIOXYGENASE7 Is Involved in the Production of Negative and Positive Branching Signals in Petunia

Abstract

One of the key factors that defines plant form is the regulation of when and where branches develop. The diversity of form observed in nature results, in part, from variation in the regulation of branching between species. Two CAROTENOID CLEAVAGE DIOXYGENASE (CCD) genes, CCD7 and CCD8, are required for the production of a branch-suppressing plant hormone. Here, we report that the decreased apical dominance3 (dad3) mutant of petunia (Petunia hybrida) results from the mutation of the PhCCD7 gene and has a less severe branching phenotype than mutation of PhCCD8 (dad1). An analysis of the expression of this gene in wild-type, mutant, and grafted petunia suggests that in petunia, CCD7 and CCD8 are coordinately regulated. In contrast to observations in Arabidopsis (Arabidopsis thaliana), ccd7ccd8 double mutants in petunia show an additive phenotype. An analysis using dad3 or dad1 mutant scions grafted to wild-type rootstocks showed that when these plants produce adventitious mutant roots, branching is increased above that seen in plants where the mutant roots are removed. The results presented here indicate that mutation of either CCD7 or CCD8 in petunia results in both the loss of an inhibitor of branching and an increase in a promoter of branching.

Strigolactones fine-tune the root system

“…Yet, early studies already reported that strigolactone shoot branching mutants in pea and petunia had reduced root biomass (Beveridge et al 1996;Snowden et al 2005;Drummond et al 2009) whereas the dry weight of other strigolactone mutants did not differ from the wild type (Beveridge et al 1997a;Morris et al 2001). In petunia strigolactone mutants, no obvious change in root structure associated with the observed reduction in root mass (Snowden et al 2005).…”

Strigolactones as mediators of plant growth responses to environmental conditions

“…3,7,[26][27][28][29], and were suggested to sequentially catalyze carotenoid cleavage reactions. 30,31 Also, a cytochrome P450 monooxygenase, MAX1, was suggested to be involved in a later biosynthetic step, 2,32 whereas additional steps in SL synthesis are anticipated yet unknown.…”

“…2,3 SL pathways have so far been identified in several plant species, including Arabidopsis thaliana, rice (Oryza sativa), petunia (Petunia hybrid), pea (Pisum sativum), tomato (Solanum lycopersicum) and chrysanthemum (Dendranthema grandiflorum) 2,3,[26][27][28] (reviewed in ref. 7 and 29).…”

Diverse Roles of Strigolactone Signaling in Maize Architecture and the Uncoupling of a Branching-Specific Subnetwork

“…These include the more axillary growth (max) mutants of Arabidopsis (Arabidopsis thaliana; Sorefan et al, 2003;Booker et al, 2004), ramosus (rms) mutants of pea (Pisum sativum; Foo et al, 2005), decreased apical dominance (dad) mutants of petunia (Petunia hybrida; Snowden et al, 2005;Drummond et al, 2009), and the dwarf (d) and high tillering dwarf (htd) mutants of rice (Oryza sativa; Zou et al, 2006;Arite et al, 2007). That SLs are derived from carotenoids was first established by analyses of maize carotenoid-deficient mutants (Matusova et al, 2005).…”