Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the Solanaceae, self-incompatibility is controlled by a single, multi-allelic ('S') locus. One product of this locus is a ribonuclease, the S-RNase, which is expressed predominantly in mature pistils and has recently been shown to cause allele-specific pollen rejection in transgenic plants. Hybrid Nicotiana plumbaginifolia x N. alata plants were used to test the effects of antisense suppression of the SA2-RNase from N. alata using three different gene constructs: two driven by RNA polymerase II-transcribed promoters, and the third, containing a truncated soybean tRNA (met-i) gene, transcribed by RNA polymerase III. All three constructs caused suppression of S-RNase activity in the transgenic plants. Unexpectedly, the CaMV 35S promoter was more effective for antisense suppression than the tissue specific tomato ChiP promoter. Antisense suppression of S-RNase correlated with low sense SA2 transcript levels and high antisense SA2 transcript levels. Untransformed hybrids that contained the N. alata SA2 allele were incompatible with N. alata SA2 pollen, while transgenic plants with suppressed SA2 gene expression accepted the pollen. The utility of this hybrid plant system for studying some aspects of antisense gene suppression is discussed.
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PMID:Antisense suppression of S-RNase expression in Nicotiana using RNA polymerase II- and III-transcribed gene constructs. 757 73

In self-incompatible plants of the Solanaceae, the specificity of pollen rejection is controlled by a single multiallelic S-locus. Pollen tube growth is inhibited in the style when its single S-allele matches either S-allele present in the diploid pistil. Each S-allele encodes an S-RNase with a unique sequence. S-RNases are secreted into the extra-cellular matrix of the transmitting tract which guides pollen tubes toward the ovary. Although it is known that S-RNases are the determinants of S-allele specificity in the pistil, it is not known how allele-specific information is encoded in the sequence. Therefore, we exchanged domains between S-RNases with different recognition specificities and expressed the chimeric proteins in transgenic plants to determine their effects on pollination behavior. Nine chimeric constructs were prepared in which domains from Nicotiana alata SA2- and SC10-RNases were exchanged. Among these nine constructs, the entire S-RNase sequence was sampled by exchanging single variable domains as well as larger blocks of contiguous sequences. The chimeric S-RNases retained enzymatic activity and were expressed at levels comparable to control transformants expressing SA2- and SC10-RNases. However, none of the chimeric S-RNases caused rejection of either SA2- or SC10-pollen. We conclude that the recognition function of S-RNases can be disrupted by alterations in many parts of the sequence. It appears that the recognition function of S-RNase is not localized to a specific domain.
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PMID:Exchanging sequence domains between S-RNases from Nicotiana alata disrupts pollen recognition. 916 Oct 37

Unilateral incompatibility often occurs between self-incompatible (SI) species and their self-compatible (SC) relatives. For example, SI Nicotiana alata rejects pollen from SC N. plumbaginifolia, but the reciprocal pollination is compatible. This interspecific pollen rejection system closely resembles intraspecific S-allele-specific pollen rejection. However, the two systems differ in degree of specificity. In SI, rejection is S-allele-specific, meaning that only a single S-RNase causes rejection of pollen with a specific S genotype. Rejection of N. plumbaginifolia pollen is less specific, occurring in response to almost any S-RNase. Here, we have tested whether a non-S-RNase can cause rejection of N. plumbaginifolia pollen. The Escherichia coli rna gene encoding RNAseI was engineered for expression in transgenic (N. plumbaginifolia x SC N. alata) hybrids. Expression levels and pollination behavior of hybrids expressing E. coli RNaseI were compared to controls expressing SA2-RNase from N. alata. Immunoblot analysis and RNase activity assays showed that RNaseI and SA2-RNase were expressed at comparable levels. However, expression of SA2-RNase caused rejection of N. plumbaginifolia pollen, whereas expression of RNaseI did not. Thus, in this system, RNase activity alone is not sufficient for rejection of N. plumbaginifolia pollen. The results suggest that S-RNases may be specially adapted to function in pollen rejection.
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PMID:RNaseI from Escherichia coli cannot substitute for S-RNase in rejection of Nicotiana plumbaginifolia pollen. 948 50

In self-incompatible (SI) plants, the S locus acts to prevent growth of self-pollen and thus promotes outcrossing within the species. Interspecific crosses between SI and self-compatible (SC) species often show unilateral incompatibility that follows the SI x SC rule: SI species reject pollen from SC species, but the reciprocal crosses are usually compatible. The general validity of the SI x SC rule suggests a link between SI and interspecific pollen rejection; however, this link has been questioned because of a number of exceptions to the rule. To clarify the role of the S locus in interspecific pollen rejection, we transformed several Nicotiana species and hybrids with genes encoding SA2 or SC10 RNase from SI N. alata. Compatibility phenotypes in the transgenic plants were tested using pollen from three SC species showing unilateral incompatibility with N. alata. S RNase was implicated in rejecting pollen from all three species. Rejection of N. plumbaginifolia pollen was similar to S allele-specific pollen rejection, showing a requirement for both S RNase and other genetic factors from N. alata. In contrast, S RNase-dependent rejection of N. glutinosa and N. tabacum pollen proceeded without these additional factors. N. alata also rejects pollen from the latter two species through an S RNase-independent mechanism. Our results implicate the S locus in all three systems, but it is clear that multiple mechanisms contribute to interspecific pollen rejection.
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PMID:S RNase and Interspecific Pollen Rejection in the Genus Nicotiana: Multiple Pollen-Rejection Pathways Contribute to Unilateral Incompatibility between Self-Incompatible and Self-Compatible Species. 1223 7