Expression of auxin‐inducible genes in relation to endogenous indoleacetic acid (IAA) levels in wild‐type and IAA‐overproducing transgenic tobacco plants

Abstract

Probes corresponding to the auxin‐inducible genes parA and parB, as well as two aux genes, here denoted Nt‐aux8 and Nt‐aux16, were amplified from tobacco (Nicotiana tabacum L.) cDNA. Transcript levels of these genes were analysed in wild‐type tobacco plants and in the transgenic IAA‐overproducing line C, and related to the endogenous IAA level. In addition, effects of naphtyl‐1‐acetic acid (NAA) treatment on the expression of these genes were determined in both genotypes. Two separate situations were identified. Nt‐aux8 and Nt‐aux16 steady‐state mRNA levels were positively correlated with the IAA content in wild‐type and line C plants. Addition of NAA induced these two genes strongly in wild‐type plants, but only slightly in line C plants. On the other hand, mRNA levels of the parA and parB genes varied more with the organ analysed and its age than with the IAA level, and were induced by NAA treatment to a similar extent in the two genotypes. The results suggest that expression of the two Nt‐aux genes is closely related to the endogenous auxin level, whereas expression of the parA and parB genes to a greater extent is influenced by additional factors.

Molecular Cloning and Expression of The Early Auxin-Responsive Aux/IAA Gene Family in Nicotiana tabacum

“…This led to the cloning of two partial cDNAs denoted Nt-aux8 and Nt-auxl6, which displayed 17% nucleotide identity with the soybean cDNA clone Aux28, and 15% identity with the mung bean Arg4 sequence, respectively (Sitbon et al 1996). To obtain the corresponding fulllength cDNAs, these two fragments were successively used to screen a cDNA library from auxin-treated seedlings.…”

“…Two PCR fragments corresponding to distinct members of the tobacco Aux/IAA gene family, previously named Nt-aux8 and Nt-auxl6 (Sitbon et al 1996), as well as the AK3-2 fragment, isolated by differential display (Roux et al 1998), were used to screen the cDNA library. A total of 200,000 or 300,000 recombinant plaques were screened with the radiolabelled Nt-aux fragments and the AK3-2 insert by plaque hybridization on nylon discs.…”

Uptake, Distribution, and Metabolism of 1-Naphthaleneacetic Acid and Indole-3-Acetic Acid During Callus Initiation From Actinidia deliciosa Tissues

“…Consequently, the free and active levels of NAA are not the result of NAA uptake, but NAA metabolism must be taken into account (Barendse et al 1987). On the other hand, to assess the physiologic relevance to studies that use exogenously added auxins, increased knowledge is needed about the naturally occurring distributions and fluctuations of endogenous auxins in tissues (Sitbon et al 1996).…”