Szewińska Joanna, Simińska Joanna, Bielawski Wiesław
Warsaw University of Life Sciences-SGGW, Faculty of Agriculture and Biology, Department of Biochemistry, Nowoursynowska 159 street, Warsaw 02-776, Poland.
Warsaw University of Life Sciences-SGGW, Faculty of Agriculture and Biology, Department of Biochemistry, Nowoursynowska 159 street, Warsaw 02-776, Poland.
J Plant Physiol. 2016 Dec 1;207:10-21. doi: 10.1016/j.jplph.2016.09.008. Epub 2016 Oct 20.
Proteolysis is an important process for development and germination of cereal seeds. Among the many types of proteases identified in plants are the cysteine proteases (CPs) of the papain and legumain families, which play a crucial role in hydrolysing storage proteins during seed germination as well as in processing the precursors of these proteins and the inactive forms of other proteases. Moreover, all of the tissues of cereal seeds undergo progressive degradation via programed cell death, which is integral to their growth. In view of the important roles played by proteases, their uncontrolled activity could be harmful to the development of seeds and young seedlings. Thus, the activities of these enzymes are regulated by intracellular inhibitors called phytocystatins (PhyCys). The phytocystatins inhibit the activity of proteases of the papain family, and the presence of an additional motif in their C-termini allows them to also regulate the activity of members of the legumain family. A balance between the levels of cysteine proteases and phytocystatins is necessary for proper cereal seed development, and this is maintained through the antagonistic activities of gibberellins (GAs) and abscisic acid (ABA), which regulate the expression of the corresponding genes. Transcriptional regulation of cysteine proteases and phytocystatins is determined by cis-acting elements located in the promoters of these genes and by the expression of their corresponding transcription factors (TFs) and the interactions between different TFs.
蛋白质水解是谷类种子发育和萌发的重要过程。在植物中鉴定出的众多蛋白酶类型中，木瓜蛋白酶家族和豆天冬氨酸蛋白酶家族的半胱氨酸蛋白酶（CPs）在种子萌发期间水解储存蛋白以及加工这些蛋白质的前体和其他蛋白酶的无活性形式方面发挥着关键作用。此外，谷类种子的所有组织都通过程序性细胞死亡进行渐进性降解，这是其生长不可或缺的一部分。鉴于蛋白酶发挥的重要作用，其不受控制的活性可能对种子和幼苗的发育有害。因此，这些酶的活性由称为植物胱抑素（PhyCys）的细胞内抑制剂调节。植物胱抑素抑制木瓜蛋白酶家族蛋白酶的活性，并且它们C末端中额外基序的存在使它们也能够调节豆天冬氨酸蛋白酶家族成员的活性。半胱氨酸蛋白酶和植物胱抑素水平之间的平衡对于谷类种子的正常发育是必要的，并且这通过赤霉素（GAs）和脱落酸（ABA）的拮抗活性来维持，它们调节相应基因的表达。半胱氨酸蛋白酶和植物胱抑素的转录调控由位于这些基因启动子中的顺式作用元件以及它们相应转录因子（TFs）的表达和不同TFs之间的相互作用决定。
