| RT-PCR |
roots |
up-regulated |
N/A |
Mt4 is a cDNA representing a phosphate-starvation-inducible gene from Medicago truncatula that is down-regulated in roots in response to inorganic phosphate (Pi) fertilization and colonization by arbuscular mycorrhizal fungi. The expression of the Mt4 gene in M.truncatula roots is down-regulated systemically by both Pi fertilization and colonization by arbuscular mycorrhizal fungi. Analysis of the expression of the Mt4-like Arabidopsis gene, At4, in wild-type Arabidopsis and pho1, a mutant unable to load Pi into the xylem, suggests that Pi must first be translocated to the shoot for down-regulation to occur. The data from the pho1 and split-root studies are consistent with the presence of a translocatable shoot factor responsible for mediating the systemic downregulation of Mt4-like genes in roots. (Burleigh et al., 1999) Mt4, a phosphate starvation inducible cDNA from Medicago truncatula which is down-regulated in roots in response to phosphate fertilization as well as colonization by arbuscular mycorrhizal (AM) fungi. Expression was highly sensitive to exogenous applications of phosphate fertilizer; transcripts were abundant in roots fertilized with nutrient solution lacking phosphate. Mt4 is the first cDNA reported to show independent regulation by both phosphate and mycorrhizal fungi. Mt4 gene expression exhibited an inverse, exponential correlation with soluble phosphorus levels in the leaves. The Mt4 gene from M.truncatulais the first plant gene identified whose expression is down-regulated by both phosphate starvation and mycorrhizal colonization and as such may provide the means to elucidate the signal transduction pathways involved in these two processes. The phosphate fertilization experiment indicated that Mt4 gene expression in roots was maximal under conditions of P-starvation and dramatically reduced by relatively low levels of phosphate fertilization. The response of Mt4 expression to P-starvation was similar to that of MtPT2, a P-starvation inducible phosphate transporter from M.truncatula. (Burleigh et al., 1998) A cDNA clone (Mt4) was isolated as a result of a differential screen to identify genes showing altered expression during the interaction between Medicago truncatula and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus versiforme. Mt4 represents a M.truncatula mRNA that contains numerous short open reading frames, the two longest of which are predicted to encode polypeptides of 51 amino acids each. One of these open reading frames shares a short region of identity with a phosphate starvation-inducible gene from tomato. Mt4 gene expression is regulated in response to colonization by mycorrhizal fungi: transcripts were detected in non-colonized roots and levels decreased in both M.truncatula and M.sativa(alfalfa) roots after colonization by G.versiforme. Northern blot analyses indicate that Mt4 transcripts are present primarily in roots and barely detectable in stems or leaves, Thus, Mt4 represents a M.truncatula gene whose expression is regulated in response to both colonization by mycorrhizal fungi and to the phosphate status of the plant. (Burleigh et al., 1997) |
9880366, 9207836 |
PLNlncRbase
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