Derba-Maceluch Marta, Awano Tatsuya, Takahashi Junko, Lucenius Jessica, Ratke Christine, Kontro Inkeri, Busse-Wicher Marta, Kosik Ondrej, Tanaka Ryo, Winzéll Anders, Kallas Åsa, Leśniewska Joanna, Berthold Fredrik, Immerzeel Peter, Teeri Tuula T, Ezcurra Ines, Dupree Paul, Serimaa Ritva, Mellerowicz Ewa J
Department of Forest Genetics and Plant Physiology, SLU, Umeå Plant Science Centre (UPSC), Umeå, Sweden.
New Phytol. 2015 Jan;205(2):666-81. doi: 10.1111/nph.13099. Epub 2014 Oct 13.
Certain xylanases from family GH10 are highly expressed during secondary wall deposition, but their function is unknown. We carried out functional analyses of the secondary-wall specific PtxtXyn10A in hybrid aspen (Populus tremula × tremuloides). PtxtXyn10A function was analysed by expression studies, overexpression in Arabidopsis protoplasts and by downregulation in aspen. PtxtXyn10A overexpression in Arabidopsis protoplasts resulted in increased xylan endotransglycosylation rather than hydrolysis. In aspen, the enzyme was found to be proteolytically processed to a 68 kDa peptide and residing in cell walls. Its downregulation resulted in a corresponding decrease in xylan endotransglycosylase activity and no change in xylanase activity. This did not alter xylan molecular weight or its branching pattern but affected the cellulose-microfibril angle in wood fibres, increased primary growth (stem elongation, leaf formation and enlargement) and reduced the tendency to form tension wood. Transcriptomes of transgenic plants showed downregulation of tension wood related genes and changes in stress-responsive genes. The data indicate that PtxtXyn10A acts as a xylan endotransglycosylase and its main function is to release tensional stresses arising during secondary wall deposition. Furthermore, they suggest that regulation of stresses in secondary walls plays a vital role in plant development.
某些来自GH10家族的木聚糖酶在次生壁沉积过程中高表达，但其功能尚不清楚。我们对杂交白杨（Populus tremula × tremuloides）中次生壁特异性的PtxtXyn10A进行了功能分析。通过表达研究、在拟南芥原生质体中过表达以及在白杨中下调表达来分析PtxtXyn10A的功能。在拟南芥原生质体中过表达PtxtXyn10A导致木聚糖内转糖基化增加而非水解。在白杨中，该酶被蛋白水解加工成一个68 kDa的肽段并存在于细胞壁中。其下调导致木聚糖内转糖基酶活性相应降低，而木聚糖酶活性没有变化。这并没有改变木聚糖的分子量或其分支模式，但影响了木纤维中的纤维素微纤丝角，增加了初生生长（茎伸长、叶片形成和扩大）并降低了形成张力木的倾向。转基因植物的转录组显示张力木相关基因下调以及应激反应基因发生变化。数据表明PtxtXyn10A作为一种木聚糖内转糖基酶，其主要功能是释放次生壁沉积过程中产生的拉伸应力。此外，它们表明次生壁中应力的调节在植物发育中起着至关重要的作用。
