Coordinated regulation of genes under phosphate starvation in plants
Abstract
Phosphate (Pi) is one of the major essential nutrients that is least available in soil. The adaptations of plants to phosphate limiting conditions involve coordinated expression of genes. Altered gene expression is presumed to be due to the interaction of cis-regulatory elements with DNA binding factors (trans-factors). As a part of our goal to understand transcriptional regulation of phosphate starvation induced genes, we analyzed the interactions between nuclear proteins and promoter fragments of AtPT2 and TPSI1, by gel retardation studies. These studies indicate that specific regions of AtPT2 and TPSI1 promoters interact with nuclear factors. Interestingly, the DNA binding protein factors disappeared during Pi starvation, leading to the hypothesis that phosphate-starvation induced genes may be under negative regulation. One of the early molecular responses to Pi deficiency is the production of phosphate transporters. By searching public databases we have identified twelve phosphate transporters in Arabidopsis. These clones probably represent the majority of members of the plant phosphate transporter multi-gene family in Arabidopsis. At least four of them were induced under phosphate starvation. Expression analysis indicated that AtPT1 and 2 are the prominent transcripts found under Pi starvation. They exhibited both temporal and spatial pattern of expression under Pi deficiency. The tissue specific expression and transcriptional regulation of Pi transporters during phosphate starvation was further analyzed with reporter genes. Transgenic plants expressing the reporter genes β-glucuronidase (GUS) and green fluorescent protein (GFP) under the regulation of AtPT1 and AtPT2 promoters were generated. The GUS expression was evident in the root tissue of Pi starved Arabidopsis plants. In these plants a strong expression of GUS was observed in the lateral roots followed by a generalized expression throughout the roots. There was a lack of expression of reporter in the tips and meristematic regions of the root. Our studies provide confirmatory evidence for the transcriptional regulation of phosphate starvation induced genes. The results also support the hypothesis that Pi starvation induced genes may be under negative regulation.
Degree
Ph.D.
Advisors
Raghothama, Purdue University.
Subject Area
Molecular biology
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