Dipartimento di Scienze e Tecnologie per l'Agricoltura, le Foreste, la Natura e l'Energia, DAFNE, Università della Tuscia, Viterbo, Italy.
Plant Biol (Stuttg). 2012 Mar;14(2):365-73. doi: 10.1111/j.1438-8677.2011.00508.x. Epub 2011 Sep 13.
Pectin is an important component of the plant cell wall and its remodelling occurs during normal plant growth or following stress responses. Pectin is secreted into the cell wall in a highly methyl-esterified form and subsequently de-methyl-esterified by pectin methyl esterase (PME), whose activity is controlled by the pectin methyl esterase inhibitor protein (PMEI). Cereal cell wall contains a low amount of pectin; nonetheless the level and pattern of pectin methyl esterification play a primary role during development or pathogen infection. Since few data are available on the role of PMEI in plant development and defence of cereal species, we isolated and characterised three Pmei genes (Tdpmei2.1, Tdpmei2.2 and Tdpmei3) and their encoded products in wheat. Sequence comparisons showed a low level of intra- and inter-specific sequence conservation of PMEIs. Tdpmei2.1 and Tdpmei2.2 share 94% identity at protein level, but only 20% identity with the product of Tdpmei3. All three Tdpmei genes code for functional inhibitors of plant PMEs and do not inhibit microbial PMEs or a plant invertase. RT-PCR analyses demonstrated, for the first time to our knowledge, that Pmei genes are regulated by intron retention. Processed and unprocessed transcripts of Tdpmei2.1 and Tdpmei2.2 accumulated in several organs, but anthers contained only mature transcripts. Tdpmei3 lacks introns and its transcript accumulated mainly in stem internodes. These findings suggest that products encoded by these Tdpmei genes control organ- or tissue-specific activity of specific PME isoforms in wheat.
果胶是植物细胞壁的重要组成部分，其重塑发生在正常的植物生长或应激反应之后。果胶以高度甲酯化的形式分泌到细胞壁中，随后被果胶甲酯酶（PME）去甲酯化，其活性受果胶甲酯酶抑制剂蛋白（PMEI）的控制。谷物细胞壁中果胶含量低；然而，果胶甲酯化的水平和模式在发育或病原体感染过程中起着主要作用。由于关于 PMEI 在谷类植物发育和防御中的作用的数据很少，我们在小麦中分离并鉴定了三个 Pmei 基因（Tdpmei2.1、Tdpmei2.2 和 Tdpmei3）及其编码产物。序列比较表明，PMEIs 的种内和种间序列保守性较低。Tdpmei2.1 和 Tdpmei2.2 在蛋白质水平上具有 94%的同源性，但与 Tdpmei3 的产物仅具有 20%的同源性。这三个 Tdpmei 基因都编码植物 PME 的功能性抑制剂，不抑制微生物 PME 或植物转化酶。RT-PCR 分析首次表明，Pmei 基因受内含子保留调控。Tdpmei2.1 和 Tdpmei2.2 的加工和未加工转录本在多个器官中积累，但花药仅含有成熟的转录本。Tdpmei3 不含内含子，其转录本主要在茎节间积累。这些发现表明，这些 Tdpmei 基因编码的产物控制小麦中特定 PME 同工型的器官或组织特异性活性。
