Selective transcriptional down-regulation of anther invertases precedes the failure of pollen development in water-stressed wheat

Abstract

Water deficit during male meiosis in wheat (Triticum aestivum L.) causes pollen sterility. With a view to identifying the internal trigger for this failure, it was found that water stress specifically impairs the activities of vacuolar and cell-wall invertases in anthers prior to the arrest of pollen development. The enzymes are affected only when water deficit occurs around meiosis. Three invertase cDNAs, two encoding the cell-wall (Ivr1, Ivr3) and one the vacuolar (Ivr5) isoform, were isolated from an anther cDNA library. RNA gel-blot analysis using floral organs of well-watered plants revealed that these genes were expressed preferentially, though not exclusively, in anthers. Semi-quantitative RT-PCR demonstrated that transitory water deficit during meiosis selectively down-regulated the transcription of two of the three genes, one encoding the vacuolar (Ivr5) and the other a cell-wall (Ivr1) isoform, without affecting the Ivr3 message. Their expression did not recover upon resumption of watering. Another homologue of Ivr1 was also down-regulated, but only during the post-stress period. The stress effects on invertase transcripts were consistent with those on the developmental profiles of the corresponding enzyme activities. In situ hybridization revealed that the stress-sensitive invertase genes, unlike an insensitive one, were expressed within the microspores. No evidence for an invertase inhibitor under stress was found. Together the results show that the decline in invertase activity is probably regulated primarily at the transcriptional level in a gene- and cell-specific manner.

Yield enhancement of droughted wheat by film antitranspirant application: rationale and evidence

“…Drought at this stage leads to pollen sterility and lower yield through reduced seed set. Drought-induced pollen sterility has been linked to reduced invertase activity, which in turn appears to result from water stress effects on transcription of genes coding for invertase [23]. No data on the mechanism by which film antitranspirant increases yield has been collected in our study, but it can be speculated that this may have occurred through a reduction in drought-induced pollen sterility.…”

TILLING Mutants of Lotus japonicus Reveal That Nitrogen Assimilation and Fixation Can Occur in the Absence of Nodule-Enhanced Sucrose Synthase

“…Vacuolar and cell wall acid invertases have essential roles in cell expansion (Sergeeva et al, 2006) and pollen development (Koonjul et al, 2005;Oliver et al, 2005) in several species, but there is general agreement that acid invertase is unlikely to be responsible for the metabolism of Suc, which provides ATP and reductant in nodule cells (Gordon et al, 1999). Supporting this, acid invertase transcripts have not been identified from nodule EST libraries of Lotus japonicus and only very low acid invertase activities have been detected in this organ (Flemetakis et al, 2006).…”

Yield stability for cereals in a changing climate

“…PCD is a process that is also responsible for pollen abortion in cytoplasmic male sterile lines in rice (Li et al 2004). The capacity of the tapetum to download sugars for pollen development is downregulated, consistent with repression in cell wall invertase gene expression in rice and wheat (Sheoran and Saini 1996;Koonjul et al 2005;Ji et al 2010). In drought- tolerant wheat, maintaining sugar transport to pollen and cell wall invertase expression is correlated with drought tolerance .…”