Chitinase-like protein CTL1 plays a role in altering root system architecture in response to multiple environmental conditions.
Plant root architecture is highly responsive to changes in nutrient availability. However, the molecular mechanisms governing the adaptability of root systems to changing environmental conditions is poorly understood. A screen for abnormal root architecture responses to high nitrate in the growth medium was carried out for a population of ethyl methanesulfonate-mutagenized Arabidopsis (Arabidopsis thaliana). The growth and root architecture of the arm (for anion altered root morphology) mutant described here was similar to wild-type plants when grown on low to moderate nitrate concentrations, but on high nitrate, arm exhibited reduced primary root elongation, radial swelling, increased numbers of lateral roots, and increased root hair density when compared to the wild-type control. High concentrations of chloride and sucrose induced the same phenotype. In contrast, hypocotyl elongation in the dark was decreased independently of nitrate availability. Positional cloning identified a point mutation in the AtCTL1 gene that encodes a chitinase-related protein, although molecular and biochemical analysis showed that this protein does not possess chitinase enzymatic activity. CTL1 appears to play two roles in plant growth and development based on the constitutive effect of the arm mutation on primary root growth and its conditional impact on root architecture. We hypothesize that CTL1 plays a role in determining cell wall rigidity and that the activity is differentially regulated by pathways that are triggered by environmental conditions. Moreover, we show that mutants of some subunits of the cellulose synthase complex phenocopy the conditional effect on root architecture under nonpermissive conditions, suggesting they are also differentially regulated in response to a changing environment.
Hermans
Christian
C
Department of Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
Porco
Silvana
S
Verbruggen
Nathalie
N
Bush
Daniel R
DR
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D020869:Gene Expression Profiling; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development*; D017354:Point Mutation; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism
D029681:Arabidopsis Proteins; D002712:Chlorides; D018744:DNA, Plant; D009566:Nitrates; D013395:Sucrose; C455513:CTL1 protein, Arabidopsis; D006026:Glycoside Hydrolases; D002688:Chitinases