| Southern blot |
Nodule formation |
down-regulated |
N/A |
ENOD40, an early nodulin gene, is expressed following inoculation with Rhizobium meliloti or by adding R.meliloti-produced nodulation (Nod) factors or the plant hormone cytokinin to uninoculated roots. We isolated two MsENOD40 clones, designated MsENOD40–1 and MsENOD40–2, with distinct promoters from an alfalfa (Medicago sativa cv Chief) genomic library. The promoters were fused to the reporter gene uidA (gus), and the constructs were introduced into alfalfa. We observed that the MsENOD40–1 construct was expressed almost exclusively under symbiotic conditions. The MsENOD40–2 construct was transcribed under both symbiotic and nonsymbiotic conditions and in nonnodular and nodular tissues. In contrast, the expression of MsENOD40–2 is likely to be constitutive, because the promoter construct was expressed in the vascular tissues of the root and the stem even in the absence of R. meliloti (see Fig. 3). In addition, the expression of the MsENOD40–2 promoter construct was also detected at the root tip and throughout lateral root development (Fig. 3). Moreover, MsENOD40–2 was expressed in the root tip, including the root cap in some transgenic plants. The expression of MsENOD40–1 as well as MsENOD40–2 was induced by BAP or Nod factor treatment, and the extent of induction is similar for both genes (2- to 3-fold), although the basal level of MsENOD40–2 expression is generally higher (Fig. 6). In addition, both genes were also expressed in a similar pattern in roots following treatment with cytokinin or Nod factor for 4d (see Fig. 3, G–Q). |
9449836 |
PLNlncRbase
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