Genome-wide identification, characterization and expression pattern analysis of APYRASE family members in response to abiotic and biotic stresses in wheat

Abstract

APYRASEs, which directly regulate intra- and extra-cellular ATP homeostasis, play a pivotal role in the regulation of various stress adaptations in mammals, bacteria and plants. In the present study, we identified and characterized wheat APYRASE family members at the genomic level in wheat. The results identified a total of nine APY homologs with conserved ACR domains. The sequence alignments, phylogenetic relations and conserved motifs of wheat APYs were bioinformatically analyzed. Although they share highly conserved secondary and tertiary structures, the wheat APYs could be mainly categorized into three groups, according to phylogenetic and structural analysis. Additionally, these APYs exhibited similar expression patterns in the root and shoot, among which TaAPY3-1, TaAPY3-3 and TaAPY3-4 had the highest expression levels. The time-course expression patterns of the eight APYs in response to biotic and abiotic stress in the wheat seedlings were also investigated. TaAPY3-2, TaAPY3-3, TaAPY3-4 and TaAPY6 exhibited strong sensitivity to all kinds of stresses in the leaves. Some APYs showed specific expression responses, such as TaAPY6 to heavy metal stress, and TaAPY7 to heat and salt stress. These results suggest that the stress-inducible APYs could have potential roles in the regulation of environmental stress adaptations. Moreover, the catalytic activity of TaAPY3-1 was further analyzed in the in vitro system. The results showed that TaAPY3-1 protein exhibited high catalytic activity in the degradation of ATP and ADP, but with low activity in degradation of TTP and GTP. It also has an extensive range of temperature adaptability, but preferred relatively acidic pH conditions. In this study, the genome-wide identification and characterization of APYs in wheat were suggested to be useful for further genetic modifications in the generation of high-stress-tolerant wheat cultivars.

Recent Advances Clarifying the Structure and Function of Plant Apyrases (Nucleoside Triphosphate Diphosphohydrolases)

“…Two other APYs that were purified and biochemically characterized recently are those of poplar [ 35 ] and wheat [ 17 ]. The purified poplar apyrase, PeAPY2, favored ATP as a substrate and had a K M of 390 µM.…”

“…Among the nine APYs genetically identified in wheat, the one biochemically characterized was the TaAPY3-1 protein, which was purified from a preparation heterologously expressed in Escherichia. coli without its transmembrane domain [ 17 ]. It had high catalytic activity for the hydrolysis of ATP and ADP, but it degraded TTP and GTP poorly.…”

“…Abiotic and biotic stresses are often accompanied by growth inhibition and these stresses also regulate expression of APYs. For example, a study by Liu et al [ 17 ] characterized the APY gene family in wheat and found their expression was differentially regulated by both abiotic and biotic stresses. A 12-h exposure to 300 mM NaCl upregulated all members of the gene family in wheat leaves, and several of them were rapidly upregulated also in wheat roots by the same treatment [ 17 ].…”

“…For example, a study by Liu et al [ 17 ] characterized the APY gene family in wheat and found their expression was differentially regulated by both abiotic and biotic stresses. A 12-h exposure to 300 mM NaCl upregulated all members of the gene family in wheat leaves, and several of them were rapidly upregulated also in wheat roots by the same treatment [ 17 ]. These results may indicate that APYs play an important role in salt stress responses in wheat, though further studies would be needed to resolve if and how they help plants overcome this stress.…”

“…In legumes the main APYs studied are those in peas [ 13 , 14 ] and soybeans [ 15 , 16 ]. A recent report on another APY family revealed that there are nine different family members in wheat, and it provided novel information on the identification, characterization and role in stress responses of these monocot APYs [ 17 ]. Apyrases have been studied in many more plants than in potato, Arabidopsis , legumes and wheat, and there have been significant advances in understanding their structures and functions in recent years.…”