碩士 / 國立中興大學 / 生命科學系所 / 99 / The plant hormone auxin is a small molecule regulates growth and development in response to environmental signals. There are many auxin-transport proteins localized to the plasma membrane. The polar localization of pin-formed (PIN) on plasma membrane affects the direction of polar auxin transport, while PINs are not always localized to the plasma membrane. PINs pass different endosomes after entering endosomal system via endocytosis. When PINs target to the late endosome/multivesicular body (MVB), they may be sent back to the early endosome by the retromer complex on MVB and then recycled to the plasma membrane. As the results, the recycling pathway maintains the polar localization of PINs on plasma membrane. The sorting of vacuolar proteins by the endosomal sorting complex required for transport (ESCRT) machinery is another important sorting process taking place in MVB. Fusion of MVB with the vacuole leads to the release of vacuolar proteins into the lumen of the vacuole. AtSKD1 has recently been shown to localize on MVB and catalyze the ATP hydrolysis. Once MVB sorting is completed, atSKD1 is required for releasing the subunits of ESCRT complex from MVB by ATP hydrolysis. In this study, examining the change of polar auxin transport in antisense atSKD1 mutants, I want to comprehend the exact role of atSKD1 in polar auxin transport.
First, examining the lateral root density of 7.3.6 line, which is a line of mutant having 50% reduced expression of endogenous atSKD1, I found it is higher than wild-type to 104% without NAA treatment and lower than wild-type to 39% when treated with 0.05 μM NAA. Besides, the root hair length of 7.3.6 line was higher than wild-type to 39% and the root hair density of 7.3.6 line was higher than wild-type to 33%. The results suggested atSKD1 is involved in polar auxin transport and normal development of roots. Furthermore, after examining the expressions of auxin transport genes in 7.3.6 line, I found the expressions of several genes such as AUX1, LAX3, PIN1, PIN2, PIN3, PIN4, PIN5, PIN7, PGP1, PGP19, and ACL5 were lower than wild-type in different degrees. The results suggested atSKD1 is involved in polar auxin transport. Distinct auxin distributions between wild-type and 7.3.6 line root were observed. In 7.3.6 line, auxin did not accumulate in the stele but accumulate high amounts in root tip. Then, examining the amount of auxin in 7.3.6 line, no matter treated with NAA or not, I found the amount of auxin in 7.3.6 line was higher than that of wild-type. The results clearly indicated the participation of atSKD1 in polar auxin transport.
Next, I examined the lateral root density of 7.1.6 and 7.2.9 lines which the expression of endogenous atSKD1 was not different from wild-type. Examining the lateral root density of 7.1.6 line, it was higher than wild-type to 38% when treated with 0.2 μM NAA. However, examining the lateral root density of 7.2.9 line, it was no significant difference from wild-type. Furthermore, examining the expressions of auxin transport genes in 7.1.6 line, I found the expressions of several genes such as PIN1, PIN2, and PIN5 were lower than wild-type and the expressions of several genes such as PIN7, PGP1, and PGP19 were higher than wild-type in different degrees. Then, examining the expressions of auxin transport genes in 7.2.9 line, I found the expressions of several genes such as AUX1, LAX3, PIN1, PIN2, PIN5, PIN7, PGP19, and ACL5 were lower than wild-type in different degrees. The results showed certain changes in auxin response were detected even when the mutants expressed atSKD1 at substantial levels.
In conclusion, atSKD1 maintains the normal function of ESCRT complex and leads the retromer complex on MVB to regulate the polar localization of PINs and other auxin transport-related proteins. Therefore, the polar auxin transport continues to carry on, and the plant grows in normal circumstance.
| Identifer | oai:union.ndltd.org:TW/099NCHU5105071 |
| Date | January 2011 |
| Creators | Ting-Ting Yang, 楊婷婷 |
| Contributors | 顏宏真 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 72 |
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