Alternative processing of the maize Ac transcript in Arabidopsis

Abstract

SummaryThe successful application of the maize transposable element system AciDs as a genome mutagen in heterologous plant species has recently proved the versatility and power of this technique in plant molecular biology. However, the frequency of Ac/Ds transposition is considerably lower in Arabidopsis thaliana than in most other dicot plant species that have been studied. Since previous research has established that transcripts derived from monocot genes can be alternatively processed in dicot plants, we have investigated both the efficiency of intron splicing and poiyadenylation of the maize Ac transposase pre-mRNA in Arabidopsis thaliana, Nicotiana tabacum, Nicotiana plumbaginifolia and Zea mays. In this paper, we demonstrate that intron 4 is alternatively spliced within Arabidopsis, using cryptic 5' and 3' splice sites within the intron sequence, leading to a heterogeneous population of full length transposase transcript. Furthermore, analysis of transposase transcript polyadenylation revealed that at least four alternative poly(A) sites were utilized between introns 2 and 3, resulting in truncated transposase transcripts. Finally, by Northern blotting, we established that the truncated transposase transcript was the most abundant form of transposase message in Arabidopsis. In contrast to these findings, the alternative splicing and premature polyadenylation of Ac message in Arabidopsis was unparalleled in the other species examined. We suggest that the poor frequency of transposition of Ac in Arabidopsis may be in part due to the low quantity of correctly processed transposase transcript available in this species.

Characterization of exon skipping mutants of the COP1 gene from Arabidopsis

“…Therefore, cop1-8 3 with the single splice site mutation displayed the same pattern of splicing (exon skipping) as cop1-8 in Arabidopsis. The differences between Arabidopsis and tobacco splicing emphasize the recent finding that different plant species may show variation in their ability to recognize and splice out different introns (Jarvis et al, 1997;Martin et al, 1997).…”

Premature Polyadenylation at Multiple Sites within aBacillus thuringiensis Toxin Gene-Coding Region1

“…This contention is supported by the finding that even a transcript normally produced in one plant species can be differentially polyadenylated when it is transcribed in another. Specifically, the maize activator (Ac) transposase transcript is polyadenylated at four sites within a 200-bp region of exon 2 when it is expressed in Arabidopsis plants (Jarvis et al, 1997;Martin et al, 1997). Recognition of these poly(A ϩ ) addition sites has been suggested to contribute to the low abundance of correctly processed transposase transcripts and hence the low frequency of transposition in this plant species.…”

Trans-activation of the maize transposable element, Ds, in Brassica napus

“…5). Primers A-F and A-R are identical to primers ZZZ;aZZZ; by Martin et al (1997). Analysis of introns III and IV was performed using primers INT3-F (5′-GTCTGCGTTCAG-TGCTGGT-3′) and INT4-R (5′-CACTTGCTCACATCTGGAT-CA-3′) (Jarvis et al 1997) (see Fig.…”

“…5C). While the sizes of these products do not correspond to incomplete processing of introns III and IV, they may represent products arising from the use of alternative 5′ and 3′ splice sites within intron IV (Martin et al 1997). Alternatively, they may represent non-specific products associated with the Ac st sequences present in all groups of plants.…”

“…One of the most successful alterations involved replacing 5′ regulatory Ac sequences with strong heterologous promoters such as the CaMV 35S, Arabidopsis rbcS and T-DNA 2′ promoters (Ellis et al 1992;Grevelding et al 1992;Honma et al 1993). Another successful modification involved expressing transposase from a cDNA copy, thus avoiding problems associated with misprocessing of the Ac transcript (Ellis et al 1992;Grevelding et al 1992;Yang et al 1993;Martin et al 1997).…”