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Abstract

ACT11 represents a unique and ancient actin subclass in the complex Arabidopsis actin gene family. We have isolated and characterized the Arabidopsis ACT11 actin gene and examined its expression. Southern blotting with a 5' gene-specific probe showed that ACT11 was a single-copy gene in the genome. Northern analysis with a 3' gene-specific probe and reverse transcriptase-mediated PCR (RT-PCR) using gene-specific primers detected ACT11 mRNA at low levels in seedling, root, leaf, and silique tissue; at moderate levels in the inflorescence stem and flower; and at very high levels in pollen. The 5' region of the ACT11 gene, including the promoter region, the 5'-untranslated leader, the intron within the leader, and the first 19 actin codons, was fused to a beta-glucuronidase (GUS) reporter gene. The expression of the ACT11/GUS fusion was examined histochemically in numerous independent transgenic Arabidopsis plants. Strong ACT11/GUS activity was detected in rapidly elongating tissues and organs (e.g., etiolated hypocotyls, expanding leaves, stems) and in floral organ primordia. As the floral buds developed into mature flowers, strong GUS activity was gradually restricted to mature pollen and developing ovules. ACT11 appears to be the only Arabidopsis actin gene expressed at significant levels in ovule, embryo, and endosperm. The unique expression patterns in reproductive organs and the sequence divergence of the ACT11 actin gene suggest that the ACT11 isovariant plays distinct and required roles during Arabidopsis development.

Multiple Actin Isotypes in Plants: Diverse Genes for Diverse Roles?

“…Some actin genes, such as ACT2 and ACT8 , lack the consensus polyadenylation element AATAAA and polyadenylation is instead controlled by other sequences (An et al, 1996b). Other polyadenylation sequences often occur, such as the five polyadenylation sequences in ACT11 (Huang et al, 1997), four in ACT1 and three in ACT3 (An et al, 1996a). It has been proposed that these alternative sequences may represent a safety mechanism to avoid mRNA degradation through RNA interference, which can be induced by un-polyadenylated transcripts under strong expression (Luo and Chen, 2007).…”

“…There are almost as many substitutions in charged amino acid residues between any two subclasses in Arabidopsis as in the entire actin family in humans (Huang et al, 1997). Vertebrate cytoplasmic and muscle actins differ in about 5% of the amino acid sequence; these are represented by only a few changes in charged residues, showing much less variability than plant actins (An et al, 1996b).…”

“…ACT4/12 are expressed in young vascular tissues, tapetum, and developing and mature pollen, whereas ACT12 expression was detected also in the pericycle during lateral root initiation and early development (Huang et al, 1996a). ACT11 is the most distinct reproductive actin, with strong expression in rapidly elongating tissues, floral organ primordia, mature pollen, ovule, embryo, and endosperm (Huang et al, 1997). ACT2 was expressed in all vegetative tissues and no expression was detected for example in gynoecia or pollen sacs, whereas ACT8 expression was weaker and detectable only in a subset of tissues expressing ACT2 (An et al, 1996b).…”

Intron-Mediated Enhancement: A Tool for Heterologous Gene Expression in Plants?

“…However, IME cannot be assigned to one specific sequence element and is more likely a result of a combination of multiple factors. Predominantly, a role for C/T-stretches was proposed to facilitate IME (Huang et al, 1997; Rose and Beliakoff, 2000; Clancy and Hannah, 2002; Mun et al, 2002; Jeong et al, 2007). Additionally, IME was linked to specific sequence motifs (TTNGATYTG, Rose et al, 2008; CGATT, Parra et al, 2011) that were found in a bioinformatic approach that was based on the observation that the nucleotide composition of introns located close to TIS is different to those located further downstream in the gene body (IMEter, Rose et al, 2008).…”

The Arabidopsis transcription factor IIB-related protein BRP4 is involved in the regulation of mitotic cell-cycle progression during male gametogenesis

“…S3A at JXB online). ACT11 was expressed in young pistils from anther development stages 9–12, and was also strongly expressed in mature pollen (Huang et al , 1997). Among the 18 transgenic lines we obtained, no pollen developmental defects were observed, although a decrease in BRP4 expression was detected in the inflorescences of these transgenic plants (Supplementary Fig.…”