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oai:www.ideals.illinois.edu:2142/106459 2023-07-11 col_2142_5131 col_2142_16357 com_2142_5130 com_2142_16356 com_2142_8913 com_2142_8903

Ming, Ray Ming, Ray Heath, Katy Chen, Li-Qing Jamann, Tiffany Nguyen, Julie 2020-03-02T22:38:47Z 2020-03-02T22:38:47Z 2023-12-01T06:00:00Z 2019-12-04 2019-12 Carica papaya (papaya), a fruit cultivated in tropical and sub-tropical regions, is known for its nutritional benefits and medicinal applications. Sex in papaya is controlled by a pair of nascent sex chromosomes with two slightly different Y chromosomes that distinguish males (XY) and hermaphrodites (XYh). These two Y chromosomes diverged about 4,000 years ago with only 0.4% sequence difference between them. The hermaphrodite specific region of the Yh chromosome (HSY), its X chromosome counterpart, and the male specific region of the Y (MSY) were sequenced. This relatively small region contains the sex determination genes as well as gene responsible for sex-linked traits such as peduncle length. Carica papaya contains three types of sex chromosome-female X, male Y and hermaphrodite Yh, and the male plant is the only sex type that bears long peduncle with numerous flowers. This sexual morphology provides a reproductive advantage by optimizing male inflorescence structure to maximize the number of flowers it can bear. However, the gene(s) responsible for this male-linked trait is not identified. There are two genes that differentiate males and hermaphrodites: a carpel suppressor gene and a gene promoting the elongation of peduncle length. SHORT VEGETATIVE PHASE (CpSVP) is present in Y chromosome but absent from X chromosome and is disrupted in Yh chromosome made it one of the ideal candidate genes for controlling peduncle length or sex determination. Using Arabidopsis as a heterologous system, CpSVP-Y male allele is sub-functionalized on both pedicel length and flowering time regulation while the autosomal allele is only involved in the former function. The CpSVP-Yh allele had no effect on pedicel length or flowering time. In Arabidopsis, we studied the spatial and temporal expression of CpSVP during vegetative and reproductive stages. CpSVP-Y and CpSVP-Yh are expressed transcriptionally in the floral organs, pedicels and leaves under its native 2kb promoter regulation but only CpSVP-Y allele can cause pedicel elongation, with no defects in reproductive organs. CpSVP-A(2kb) also is expressed in the same tissues, albeit weakly in the pedicels. Under its native 1kb promoter, CpSVP-Y and CpSVP-Yh is not expressed in the floral organs and negligible expression in pedicels. We identified a GA response cis-element, a pyrimidine box (P-box) at -461 bp, that enhances CpSVP expression and pedicels with no effect on flowering time, elongating pedicels only for CpSVP-Y allele. Determining the gene responsible for peduncle elongation will enhance our understanding of sex determination and the evolution of sex chromosomes of papaya. These findings implicate that the P-box at -461 bp promoter region plays a major role in controlling the spatial and temporal expression of CpSVP-Y, which leads to peduncle length and flowering time regulation but not sex determination. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01 The student, Julie Nguyen, accepted the attached license on 2019-11-22 at 19:13. The student, Julie Nguyen, submitted this Dissertation for approval on 2019-11-26 at 10:14. This Dissertation was approved for publication on 2019-12-04 at 11:42. DSpace SAF Submission Ingestion Package generated from Vireo submission #14599 on 2020-02-28 at 17:36:45 Made available in DSpace on 2020-03-02T22:38:47Z (GMT). No. of bitstreams: 2 NGUYEN-DISSERTATION-2019.pdf: 3653739 bytes, checksum: 1a528a38004c4f81edb93c77e54962de (MD5) LICENSE.txt: 4209 bytes, checksum: 147fdfca3e814502737f73ebe94aade8 (MD5) Previous issue date: 2019-12-04 Embargo set by: Seth Robbins for item 114003 Lift date: 2022-03-02T22:39:04Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system U of I Only Restriction set for Item 114003 on 2021-12-01T19:01:47Z with date 2023-12-01 by eliasbh2@illinois.edu. U of I Only Restriction set for Item 114003 on 2021-12-01T19:01:51Z with date 2023-12-01 by eliasbh2@illinois.edu. Author requested U of I Only Access for two years through thesis office U of I Only application/pdf http://hdl.handle.net/2142/106459 en Copyright 2019 Julie Nguyen Papaya, sex chromosome evolution, peduncle elongation Functional characterization and analysis of Carica papaya SHORT VEGETATIVE PHASE (CpSVP) text text Plant Biology Plant Biology University of Illinois at Urbana-Champaign Dissertation Ph.D.