Valdés-Rodríguez Silvia, Guerrero-Rangel Armando, Melgoza-Villagómez Claudia, Chagolla-López Alicia, Delgado-Vargas Francisco, Martínez-Gallardo Norma, Sánchez-Hernández Carla, Délano-Frier John
Departamento de Biotecnología y Bioquímica, Cinvestav, Km. 9.6, Libramiento Norte, 36500, A.P. 629 Irapuato, Gto. Mexico, Mexico.
Plant Physiol Biochem. 2007 Oct-Nov;45(10-11):790-8. doi: 10.1016/j.plaphy.2007.07.007. Epub 2007 Jul 25.
A cDNA, encoding a cysteine protease inhibitor (AhCPI), was isolated from an immature seed cDNA library of grain amaranth (Amaranthus hypochondriacus L.) and characterized. It encoded a polypeptide of 247 amino acids (aa), including a putative N-terminal signal peptide. Other relevant regions found in its sequence included the G and PW conserved aa motifs, the consensus LARFAV sequence for phytocystatins and the reactive site QVVAG. The predicted aa sequence for AhCPI showed a significant homology to other plant cystatins. Gene expression analyses indicated that AhCPI was constitutively expressed in mature seeds, and gradually decreased during germination. In vegetative tissues, AhCPI was expressed in the radicle and hypocotyls of seedlings and in the stems and roots of young plantlets. Its expression in roots and stems increased substantially in response to water deficit, salinity-, cold- and heat-stress, whereas heat-stress induced a rapid and transient accumulation of AhCPI transcripts in leaves. The results obtained were suggestive of multiple roles for AhCPI in grain amaranth, acting as a regulator of seed germination and as a protective agent against diverse types of abiotic stress, which induced this gene in a tissue- and stress-specific manner. The work herewith described reports a novel, and apparently, single cystatin protein in which, in agreement with other plant model systems, could have a regulatory role in germination, and further expands previous findings linking the accumulation of protease inhibitors, mostly of the serine proteinase type, with protection against (a)biotic stress in A. hypochondriacus.
从籽粒苋（Amaranthus hypochondriacus L.）未成熟种子cDNA文库中分离并鉴定了一个编码半胱氨酸蛋白酶抑制剂（AhCPI）的cDNA。它编码一个由247个氨基酸（aa）组成的多肽，包括一个推定的N端信号肽。在其序列中发现的其他相关区域包括G和PW保守氨基酸基序、植物胱抑素的共有LARFAV序列以及活性位点QVVAG。AhCPI的预测氨基酸序列与其他植物胱抑素具有显著同源性。基因表达分析表明，AhCPI在成熟种子中组成型表达，在萌发过程中逐渐降低。在营养组织中，AhCPI在幼苗的胚根和下胚轴以及幼苗的茎和根中表达。其在根和茎中的表达在水分亏缺、盐胁迫、冷胁迫和热胁迫下显著增加，而热胁迫诱导AhCPI转录本在叶片中快速短暂积累。所得结果表明AhCPI在籽粒苋中具有多种作用，作为种子萌发的调节剂和针对多种非生物胁迫的保护剂，以组织和胁迫特异性方式诱导该基因。本文所述工作报道了一种新的、显然单一的胱抑素蛋白，与其他植物模型系统一致，它可能在萌发中具有调节作用，并进一步扩展了先前将蛋白酶抑制剂（主要是丝氨酸蛋白酶类型）的积累与籽粒苋对（非）生物胁迫的保护联系起来的研究结果。
