Seasonal and cell type specific expression of sulfate transporters in the phloem of Populus reveals tree specific characteristics for SO4 2- storage and mobilization
Seasonal and cell type specific expression of sulfate transporters in the phloem of Populus reveals tree specific characteristics for SO4 2- storage and mobilization
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DOI：
10.1007/s11103-009-9587-6
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发表时间：
2010-03-01
影响因子：
5.1
通讯作者：
Herschbach, Cornelia
中科院分区：
文献类型：
--
作者：
Duerr, Jasmin;Buecking, Heike;Herschbach, Cornelia
木材和树皮组织中营养物质的储存和动员是树木的一个典型特征。硫可以以硫酸盐的形式储存，通过韧皮部从源输送到汇组织。本研究在灰杨（Populus tremula x P. alba）韧皮部鉴定了两个硫酸盐转运蛋白（SULTR）转录本。在杨树的源组织（如成熟叶片）和汇组织（如茎、根和茎尖的木材和树皮）中分析了它们的细胞特异性表达。PtaSULTR1;在运输韧皮部的伴生细胞、高阶叶脉的韧皮部和细根中检测到1 mRNA。PtaSULTR3;3a mRNA仅存在于运输韧皮部中，同时存在于伴生细胞和筛元件中。两个硫酸盐转运蛋白转录本都位于木质部薄壁细胞中，表明PtaSULTR1的作用；1和PtaSULTR3；3a在木质部卸荷。这些和硫酸盐转运体PtaSULTR4 mRNA丰度的变化；1和PtaSULTR4；其中2个在整个生长季节进行了分析。PtaSULTR3的表达；3a和假定的液泡外排转运体PtaSULTR4；2与树皮中硫酸盐含量负相关。此外，PtaSULTR3；3a和PtaSULTR4；2与温度、日长显著相关。因此，两个SULTRs似乎都参与了春季硫酸盐的动员：PtaSULTR4；2 .介导液泡外排和PtaSULTR3；3a介导装载进入运输韧皮部。相比之下，PtaSULTR1；1和PtaSULTR4；1个转录本在整个季节中不受环境变化的影响。所有硫酸盐转运体在叶片中的转录丰度与天气条件无关。然而,PtaSULTR1;1丰度与叶片中硫酸盐含量呈负相关，支持其在韧皮部负荷中的作用。综上所述，这些发现表明硫酸盐在杨树中的分布存在转录调控。
The storage and mobilization of nutrients in wood and bark tissues is a typical feature of trees. Sulfur can be stored as sulfate, which is transported from source to sink tissues through the phloem. In the present study two transcripts encoding sulfate transporters (SULTR) were identified in the phloem of grey poplar (Populus tremula x P. alba). Their cell-specific expression was analyzed throughout poplar in source tissues, such as mature leaves, and in sink tissues, such as the wood and bark of the stem, roots and the shoot apex. PtaSULTR1;1 mRNA was detected in companion cells of the transport phloem, in the phloem of high-order leaf veins and in fine roots. PtaSULTR3;3a mRNA was found exclusively in the transport phloem and here in both, companion cells and sieve elements. Both sulfate transporter transcripts were located in xylem parenchyma cells indicating a role for PtaSULTR1;1 and PtaSULTR3;3a in xylem unloading. Changes in mRNA abundance of these and of the sulfate transporters PtaSULTR4;1 and PtaSULTR4;2 were analyzed over an entire growing season. The expression of PtaSULTR3;3a and of the putative vacuolar efflux transporter PtaSULTR4;2 correlated negatively with the sulfate content in the bark. Furthermore, the expression pattern of both PtaSULTR3;3a and PtaSULTR4;2 correlated significantly with temperature and day length. Thus both SULTRs seem to be involved in mobilization of sulfate during spring: PtaSULTR4;2 mediating efflux from the vacuole and PtaSULTR3;3a mediating loading into the transport phloem. In contrast, the abundance of PtaSULTR1;1 and PtaSULTR4;1 transcripts was not affected by environmental changes throughout the whole season. The transcript abundance of all tested sulfate transporters in leaves was independent of weather conditions. However, PtaSULTR1;1 abundance correlated negatively with sulfate content in leaves, supporting its function in phloem loading. Taken together, these findings indicate a transcriptional regulation of sulfate distribution in poplar trees.