Suppression of LX Ribonuclease in Tomato Results in a Delay of Leaf Senescence and Abscission

Lers, Amnon; Sonego, Lilian; Green, Pamela J.; Burd, Shaul

doi:10.1104/pp.106.080135

Cited by 66 publications

(61 citation statements)

References 87 publications

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“…We previously documented significant inhibition of tomato leaf abscission in LX-deficient transgenic plants (Lers et al, 2006). We examined whether or not flower abscission is also suppressed in three independent LX-inhibited tomato lines.…”

Section: Flower Abscission Is Delayed In Lx-inhibited Plantsmentioning

confidence: 99%

“…We previously showed that inhibiting expression of the ribonuclease gene LX results in retardation of leaf abscission in tomato (Lers et al, 2006). Tomato LX ribonuclease (LX) is a T2/S-like ribonuclease whose expression is known to be associated with phosphate starvation, ethylene responses, senescence, and programmed cell death (PCD) (Lers et al, 1998;Lehmann et al, 2001;Kö ck et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Programmed Cell Death Occurs Asymmetrically during Abscission in Tomato

et al. 2011

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Abscission occurs specifically in the abscission zone (AZ) tissue as a natural stage of plant development. Previously, we observed delay of tomato (Solanum lycopersicum) leaf abscission when the LX ribonuclease (LX) was inhibited. The known association between LX expression and programmed cell death (PCD) suggested involvement of PCD in abscission. In this study, hallmarks of PCD were identified in the tomato leaf and flower AZs during the late stage of abscission. These included loss of cell viability, altered nuclear morphology, DNA fragmentation, elevated levels of reactive oxygen species and enzymatic activities, and expression of PCD-associated genes. Overexpression of antiapoptotic proteins resulted in retarded abscission, indicating PCD requirement. PCD, LX, and nuclease gene expression were visualized primarily in the AZ distal tissue, demonstrating an asymmetry between the two AZ sides. Asymmetric expression was observed for genes associated with cell wall hydrolysis, leading to AZ, or associated with ethylene biosynthesis, which induces abscission. These results suggest that different abscission-related processes occur asymmetrically between the AZ proximal and distal sides. Taken together, our findings identify PCD as a key mechanism that occurs asymmetrically during normal progression of abscission and suggest an important role for LX in this PCD process.

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Section: Flower Abscission Is Delayed In Lx-inhibited Plantsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Programmed Cell Death Occurs Asymmetrically during Abscission in Tomato

et al. 2011

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“…Thousands of SAGs have been isolated, including genes encoding transcription factors, signal transduction components, proteinases and other catabolic enzymes, and various transporters of sugars, amino acids, and other nutrients (Gepstein et al, 2003;Guo et al, 2004;Buchanan-Wollaston et al, 2005;Guo and Gan, 2012). Some of these SAGs, such as NAC and WRKY transcription factor genes (Guo and Gan, 2006;Uauy et al, 2006;Zentgraf et al, 2010;Besseau et al, 2012;, protein kinase and phosphatase genes (Hajouj et al, 2000;Zhou et al, 2009;Xu et al, 2011;, lipase genes (He and Gan, 2002), and nuclease genes (Lers et al, 2006), have been shown biochemically, genetically, and/or physiologically to have a role in leaf senescence. The functions of the vast majority of SAGs (some of which encode Small Auxin Up RNAs [SAURs]) have yet to be characterized.…”

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confidence: 99%

SAUR36, a SMALL AUXIN UP RNA Gene, Is Involved in the Promotion of Leaf Senescence in Arabidopsis

2012

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Small Auxin Up RNA genes (SAURs) are early auxin-responsive genes, but whether any of them are involved in leaf senescence is not known. Auxin, on the other hand, has been shown to have a role in leaf senescence. Some of the external application experiments indicated that auxin can inhibit leaf senescence, whereas other experiments indicated that auxin can promote leaf senescence. Here, we report the identification and characterization of an Arabidopsis (Arabidopsis thaliana) leaf senescenceassociated gene named SAG201, which is highly up-regulated during leaf senescence and can be induced by 1-naphthaleneacetic acid, a synthetic auxin. It encodes a functionally uncharacterized SAUR that has been annotated as SAUR36. Leaf senescence in transfer DNA insertion saur36 knockout lines was delayed as revealed by analyses of chlorophyll content, F v /F m ratio (a parameter for photosystem II activity), ion leakage, and the expression of leaf senescence marker genes. In contrast, transgenic Arabidopsis plants overexpressing SAUR36 (without its 39 untranslated region [UTR]) displayed an early leaf senescence phenotype. However, plants overexpressing SAUR36 with its 39 UTR were normal and did not exhibit the early-senescence phenotype. These data suggest that SAUR36 is a positive regulator of leaf senescence and may mediate auxin-induced leaf senescence and that the 39 UTR containing a highly conserved downstream destabilizes the SAUR36 transcripts in young leaves.

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“…After abscission induction in plants of the 1‐7 transgenic line with inhibited LeLX expression and reduced LX protein level in which both leaf petiole and flower pedicel abscission are significantly inhibited (Lers et al . 2006; Bar‐Dror et al . 2011), at least some TAPG4 was present in the AZ (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Similar leaf‐age dependence has also been shown for induction of LX protein with external ethylene (Lers et al . 2006) and it was suggested that the phenomenon might be explained by differences in ethylene sensitivity of the AZ in different aged leaves.…”

Section: Discussionmentioning

confidence: 99%

The pattern of 1‐aminocyclopropane‐1‐carboxylate oxidase induction in the tomato leaf petiole abscission zone is independent of expression of the ribonuclease‐LX‐encoding LeLX gene

et al. 2018

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The abscission of tomato leaves occurs in the petiole abscission zone, and its late stage includes two spatially divided processes: cell separation and programmed cell death (PCD). Both of these processes are regulated by ethylene. The last step in ethylene biosynthesis is conversion of 1‐aminocyclopropane‐1‐carboxylic acid to ethylene, which is catalysed by the enzyme 1‐aminocyclopropane‐1‐carboxylate oxidase (ACO); however, the location of ACO in the leaf petiole abscission zone is not known. The tomato gene LeLX encodes ribonuclease LX, which is a marker for PCD and is induced by ethylene during abscission, but its association with ACO has not been explored.In a tomato transgenic line 1‐7 with inhibited expression of LeLX showing delayed leaf abscission, the morphology and ultrastructure of the leaf petiole abscission zone was examined. In this zone of the cv.’VF36’ and of a transgenic line 1‐7, spatiotemporal differences in expression of LeACO1 and LeACO4 were analysed and ACO protein was detected immunohistochemically.In comparison to wild‐type plants, there were no obvious morphological and ultrastructural features in the abscission zone of plants of a transgenic line 1‐7 before and after abscission induction. LeACO1 expression was low before abscission induction, and increased 24 h after induction, although with no apparent spatial pattern. In contrast, LeACO4 was expressed before abscission induction, and its transcript level declined 24 h after induction on the distal side of the abscission zone fracture. In the LeLX‐inhibited transgenic line, there were no significant differences in LeACO1 and LeACO4 expression in the petiole abscission zone, in comparison to wild‐type plants. In addition, the ACO protein was immunolocalised to the vascular tissues that traverse the petiole abscission zone in plants of wild type and of a transgenic line 1‐7; and additionally in the plane of future abscission zone fracture of transgenic‐line plants.The results suggest temporal differential expression of the LeACO genes in tomato leaf petioles and vascular localisation of ACO1 protein. Additionally, the results indicate that expression of LeACO genes is not affected by suppression of the LeLX expression.

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Suppression of LX Ribonuclease in Tomato Results in a Delay of Leaf Senescence and Abscission

Cited by 66 publications

References 87 publications

Programmed Cell Death Occurs Asymmetrically during Abscission in Tomato

Programmed Cell Death Occurs Asymmetrically during Abscission in Tomato

SAUR36, a SMALL AUXIN UP RNA Gene, Is Involved in the Promotion of Leaf Senescence in Arabidopsis

The pattern of 1‐aminocyclopropane‐1‐carboxylate oxidase induction in the tomato leaf petiole abscission zone is independent of expression of the ribonuclease‐LX‐encoding LeLX gene

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