阿拉伯芥果膠甲基酯化酶12、53、及68的功能性研究

Functional Studies of Pectin Methylesterase12, 53, and 68 in Arabidopsis

游適宇(Shih-Yu Yu)

指導教授 ： 靳宗洛

國立臺灣大學/生命科學院/植物科學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003700

摘要

植物細胞壁是一種動態結構，隨著不同環境刺激而改變以維持植物生存。果膠是初級細胞壁中三個主要組成分之一，它會被果膠甲基酯酶作用，去除果膠中聚半乳醣醛酸上的甲基。而果膠被去除甲基的程度會影響到植物體組織之彈性、柔韌性、緊密程度以及酸鹼性與帶電性。本研究發現阿拉伯芥PME12、53及68受到離層酸抑制，而PME53與68則受到誘導並在熱逆境中反應。由組織化學分析指出，PME12、53及68皆會在根、莖、葉等多個部位表現；PME53及68在ABA處理後會在氣孔大量表現。分析pme12、53及68突變株特性發現，葉部型態較小，而氣孔對ABA之反應也較敏感，且密度更高。在阿拉伯芥原生質體中短暫抑制保衛細胞生合成相關轉錄因子SCRM或MUTE也發現PME53與68表現受到下降。另外，在熱逆境處理下，pme12、53及68突變株有較高的存活率。PME12、53及68酵素活性及分析結果顯示在各種酸鹼環境中此三個酵素之最適活性不同。pme12、53及68突變株在熱處理時，細胞壁果膠去甲基化的情形也比野生型低。因此，PME12、53及68在植物體中參與保衛細胞開合、植物形態以及熱逆境反應等多種功能。

關鍵字

阿拉伯芥 ； 果膠甲基酯化酶 ； 酵素活性 ； 保衛細胞 ； 氣孔生合成路徑 ； 耐熱性

並列摘要

The plant cell wall is a dynamic structure that remodels in response to different stimuli. Pectin, one of the three major components in the primary cell wall, is modified by pectin methylesterase (PME) causing de-methylesterfied on the polygalacturonans. The degree to which pectin is de-methylesterified directly affects its rigidity, gel-forming ability, and overall porosity and influences cell wall pH and charge distribution. This study showed that the expression levels of Arabidopsis PME12 was reduced, but PME53, and PME68 were induced by abscisic acid treatments and in response to heat stress. Here, the histochemical analysies confirmed that PME12, 53 and 68 are expressed strongly in the vascular tissue of mature zone of root, cotyledon, rosette leaf, inflorescence stem, and sepal; besides, a highly-inducible expression of PME53 and PME68 in guard cells after ABA treatment was observed. We concluded that the leaf size and the pavement cells are affected in these mutant lines, and the stomatal movement in responses to ABA was more sensitive compared to the wild-type (WT); besides, the mutation of PME12, 53, or 68 caused a higher stomatal density. Transactivation analysis of the expression levels of PME53 and 68 were significantly affected through the key transcription factors in stomatal development by SCRM and MUTE. Notably, the survival rates of pme12, 53, and 68 mutant plants were significantly higher in response to HS compared to the WT plants. Physiological studies of the optimal activities of PME12, 53 and 68 were at different pH and the degrees of demethylesterfied homogalacturonans (HG) in pme12, 53, 68 were altered in response to HS. In conclusion, PME12, 53, and 68 with multiple functions that play a role in stomatal movement and patterning, in addition to regulating proper HS response.

並列關鍵字

Ababidopsis thaliana ； Pectin methylesterase ； Guard cell ； Stomatal-lineage pathway ； Thermotolerance

參考文獻

Amsbury S, Hunt L, Elhaddad N, Baillie A, Lundgren M, Verhertbruggen Y, Scheller HV, Knox JP, Fleming AJ, Gray JE. (2016). Stomatal function requires pectin de-methyl esterification of the guard cell wall. Current Biology, 2899-2906.

Ariel R.Vicente, M.L.C., Gustavo A.Martínez, Alicia R.Chaves, Pedro M.Civello. (2005). Effect of heat treatments on cell wall degradation and softening in strawberry fruit. Postharvest Biology and Technology 38, 213-222.

Boller T, Felix G. (2009). A renaissance of elicitors: perception of microbe-associated molecular patterns and danger signals by pattern-recognition receptors. Annual Review of Plant Biology 60, 379-406.

Charng YY, Liu HC, Liu NY, Hsu FC, Ko SS. (2006). Arabidopsis Hsa32, a novel heat shock protein, is essential for acquired thermotolerance during long recovery after acclimation. Plant Physiology 140, 1297-1305.

Clough SJ, Bent AF. (2008). Floral dip: a simplified method for Agrobacterium‐mediated transformation of Arabidopsis thaliana. The Plant Journal 16, 735-743.