A negative regulatory role for auxin in sulphate deficiency response in Arabidopsis thaliana.
Sulphate is a major macronutrient required for the synthesis of the sulphur (S)-containing amino acid cysteine and thus is critical for cellular metabolism, growth and development and response to various abiotic and biotic stresses. A recent genome-wide expression study suggested that several auxin-inducible genes were up-regulated by S deficiency in Arabidopsis. Here, we examined the relationship between auxin signaling and S deficiency. Investigation of DR5::GUS expression patterns indicates that auxin accumulation and/or response is suppressed by S deficiency. Consistently, S deficiency resulted in the suppression of lateral root development, but the axr1-3 mutant was insensitive to this response. Furthermore, the activation of the promoter for the putative thioglucosidase gene (At2g44460) by S deficiency was suppressed by auxin, cytokinin and abscisic acid (ABA). Interestingly, the activation of At2g44460 by S deficiency is regulated by the availability of carbon and nitrogen nutrients in a tissue-specific manner. These results demonstrate that auxin plays a negative role in signaling to S deficiency. Given that activation of the genes encoding the sulphate transporter SULTR1;2 and 5'-adenylylsulphate reductase APR2 are suppressed by cytokinin only, we hypothesize that while cytokinin may play an important role in general S deficiency response, auxin might be only involved in a subset of S deficiency responses such as the release of thiol groups from the S storage sources.
Dan
Hanbin
H
Department of Biological Sciences, Lehman College, City University of New York, Bronx, NY 10468, USA.
Yang
Guohua
G
Zheng
Zhi-Liang
ZL
D017360:Arabidopsis / Q000187:drug effects* / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D013431:Sulfates / Q000494:pharmacology*
D007210:Indoleacetic Acids; D013431:Sulfates