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

• Published in: Journal of experimental botany Vol. 56; no. 409; pp. 179 - 190
• Main Authors: Koonjul, P.K, Minhas, J.S, Nunes, C, Sheoran, I.S, Saini, H.S
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.01.2005; Oxford Publishing Limited (England)
• Subjects: Agronomy. Soil science and plant productions; Anthers; beta-fructofuranosidase; beta-Fructofuranosidase - metabolism; Biological and medical sciences; cell wall components; Complementary DNA; Dehydration; Down-Regulation - physiology; drought; Economic plant physiology; enzyme inhibitors; Enzymes; Flowers - enzymology; Fundamental and applied biological sciences. Psychology; Gametogenesis - physiology; Gene expression; gene expression regulation; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic - physiology; Gene Expression Regulation, Plant - physiology; in situ hybridization; invertase; isozymes; male sterility; Meiosis; Meiosis - physiology; messenger RNA; Microspores; Organ Specificity - physiology; plant reproduction; Plants; Pollen; Pollen - growth & development; pollen development; reproduction; Reproduction - physiology; RESEARCH PAPER; RNA; Starches; sugar metabolism; transcription (genetics); Triticum - cytology; Triticum - enzymology; Triticum aestivum; vacuoles; Water - metabolism; Water relations, transpiration, stomata; water stress; wheat; Anther; Monocotyledones; Transcription; Water deficit; β-Fructofuranosidase; Hybridization; Water stress; Cell wall; Gene; Gramineae; invertase; Angiospermae; Development; Pollen; Enzyme; sugar metabolism; Meiosis; Gene expression; pollen development; Complementary DNA; Glycosidases; Microspore; Hydrolases; Male sterility; Spermatophyta; O-Glycosidases; Triticum aestivum; reproduction
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/eri018

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.