富含丝氨酸/精氨酸(SR)蛋白是重要的剪接因子。然而,植物SR蛋白的生物学功能尚不清楚,尤其是在非生物胁迫中。镉(Cd)是一种对植物生长和发育产生负面影响的非必要元素。在这项研究中,我们为SR基因参与植物对Cd的耐受提供了明确的证据。对17个拟南芥SR基因的系统表达分析表明,SR34b是唯一被Cd上调的SR基因,表明其在拟南芥耐Cd中的潜在作用。与此一致,SR34bT-DNA插入突变体(sr34b)对Cd中度敏感,与野生型相比,具有更高的Cd(2)吸收速率和更多的Cd积累量。这是由于sr34b突变体中铁调节转运蛋白1(IRT1)基因表达的改变。在正常生长条件下,在sr34b突变体中高度积累的IRT1mRNA,这是IRT1mRNA稳定性增加的结果。在Cd胁迫下,然而,sr34b突变体植株在IRT1基因中存在剪接缺陷,从而减少IRT1mRNA的积累。尽管如此,sr34b突变植株在Cd胁迫下仍然组成型表达IRT1蛋白,从而导致Cd胁迫敏感表型。因此,我们提出了SR34b在IRT1表达的转录后调控中的重要作用,并将其鉴定为拟南芥Cd耐受性的调节剂。
Serine/arginine-rich (SR) proteins are important splicing factors. However, the biological functions of plant SR proteins remain unclear especially in abiotic stresses. Cadmium (Cd) is a non-essential element that negatively affects plant growth and development. In this study, we provided clear evidence for SR gene involved in Cd tolerance in planta. Systemic expression analysis of 17 Arabidopsis SR genes revealed that SR34b is the only SR gene upregulated by Cd, suggesting its potential roles in Arabidopsis Cd tolerance. Consistent with this, a SR34b T-DNA insertion mutant (sr34b) was moderately sensitive to Cd, which had higher Cd(2+) uptake rate and accumulated Cd in greater amounts than wild-type. This was due to the altered expression of iron-regulated transporter 1 (IRT1) gene in sr34b mutant. Under normal growth conditions, IRT1 mRNAs highly accumulated in sr34b mutant, which was a result of increased stability of IRT1 mRNA. Under Cd stress, however, sr34b mutant plants had a splicing defect in IRT1 gene, thus reducing the IRT1 mRNA accumulation. Despite of this, sr34b mutant plants still constitutively expressed IRT1 proteins under Cd stress, thereby resulting in Cd stress-sensitive phenotype. We therefore propose the essential roles of SR34b in posttranscriptional regulation of IRT1 expression and identify it as a regulator of Arabidopsis Cd tolerance.