Abstract
ANTHER INDEHISCENCE FACTOR (AIF), a NAC-like gene, was identified in Arabidopsis. In AIF:GUS flowers, β-glucuronidase (GUS) activity was detected in the anther, the upper parts of the filaments, and in the pollen of stage 7–9 young flower buds; GUS activity was reduced in mature flowers. Yellow fluorescent protein (YFP)+AIF-C fusion proteins, which lacked a transmembrane domain, accumulated in the nuclei of the Arabidopsis cells, whereas the YFP+AIF fusion proteins accumulated in the membrane and were absent in the nuclei. Further detection of a cleaved AIF protein in flowers revealed that AIF needs to be processed and released from the endoplasmic reticulum in order to function. The ectopic expression of AIF-C caused a male-sterile phenotype with indehiscent anthers throughout flower development in Arabidopsis. The presence of a repressor domain in AIF and the similar phenotype of indehiscent anthers in AIF-C+SRDX plants suggest that AIF acts as a repressor. The defect in anther dehiscence was due to the down-regulation of genes that participate in jasmonic acid (JA) biosynthesis, such as DAD1/AOS/AOC3/OPR3/OPCL1. The external application of JA rescued the anther indehiscence in AIF-C and AIF-C+SRDX flowers. In AIF-C+VP16 plants, which are transgenic dominant-negative mutants in which AIF is converted to a potent activator via fusion to a VP16-AD motif, the anther dehiscence was promoted, and the expression of DAD1/AOS/AOC3/OPR3/OPCL1 was up-regulated. Furthermore, the suppression of AIF through an antisense strategy resulted in a mutant phenotype similar to that observed in the AIF-C+VP16 flowers. The present data suggest a role for AIF in controlling anther dehiscence by suppressing the expression of JA biosynthesis genes in Arabidopsis.
Highlights
Anther dehiscence is an essential process in which mature pollen grains are released from the locules of the anther, enabling pollination
The defect in anther dehiscence was due to the down-regulation of genes that participate in jasmonic acid (JA) biosynthesis, such as DEFECTIVE IN ANTHER DEHISCENCE 1 (DAD1)/AOS/AOC3/ OPR3/OPCL1
The expression of LOX3 was down-regulated in the flowers of both 35S-Ω promoter (35S):ANTHER INDEHISCENCE FACTOR (AIF)-C and AIF-C+SRDX, its expression was unaffected in the flowers of AIF-C+VP16 (Fig. 4I). These results strongly suggest that the altered anther dehiscence in 35S:AIF-C, AIF-C+SRDX, and AIF-C+VP16 plants is correlated with the altered expression of some of the genes that participate in JA biosynthesis
Summary
Anther dehiscence is an essential process in which mature pollen grains are released from the locules of the anther, enabling pollination. Mutations in genes that participate in JA biosynthesis cause a failure or delay in anther dehiscence and can result in male sterility. Only a few works have described a possible mechanism by which the regulation of JA activity is associated with anther dehiscence (Nagpal et al, 2005; Ito et al, 2007; Cheng et al, 2009; Peng et al, 2013). One of these works describes two auxin response factors, ARF6 and ARF8, in auxin signalling that are thought to play roles in regulating JA production (Nagpal et al, 2005). The precise molecular mechanisms regulating JA activity during anther dehiscence are still to be elucidated
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