Maize proteomic responses to separate or overlapping soil drought and two-spotted spider mite stresses

Abstract

In maize, leaf proteome responses evoked by soil drought applied separately differ from those evoked by mite feeding or both types of stresses occurring simultaneously. This study focuses on the involvement of proteomic changes in defence responses of a conventional maize cultivar (Bosman) to the two-spotted spider mite infestation, soil drought and both stresses coexisting for 6 days. Under watering cessation or mite feeding applied separately, the protein carbonylation was not directly linked to the antioxidant enzymes' activities. Protein carbonylation increased at higher and lower SOD, APX, GR, POX, PPO activities following soil drought and mite feeding, respectively. Combination of these stresses resulted in protein carbonylation decrease despite the increased activity of all antioxidant enzymes (except the CAT). However, maize protein network modification remains unknown upon biotic/abiotic stresses overlapping. Here, using multivariate chemometric methods, 94 leaf protein spots (out of 358 considered; 2-DE) were identified (LC-MS/MS) as differentiating the studied treatments. Only 43 of them had individual discrimination power. The soil drought increased abundance of leaf proteins related mainly to photosynthesis, carbohydrate metabolism, defence (molecular chaperons) and protection. On the contrary, mite feeding decreased the abundance of photosynthesis related proteins and enhanced the abundance of proteins protecting the mite-infested leaf against photoinhibition. The drought and mites occurring simultaneously increased abundance of proteins that may improve the efficiency of carbon fixation, as well as carbohydrate and amino acid metabolism. Furthermore, increased abundance of the Rubisco large subunit-binding protein (subunit β), fructose-bisphosphate aldolase and mitochondrial precursor of Mn-SOD and decreased abundance of the glycolysis-related enzymes in the mite-free leaf (in the vicinity of mite-infested leaf) illustrate the involvement of these proteins in systemic maize response to mite feeding.

Keywords: Antioxidants; Simultaneous stresses; Stress-related proteins; Tetranychus urticae; Water deficiency; Zea.

Fig. 1

a–f Superoxide dismutase (SOD, a), catalase (CAT, b), ascorbate peroxidase (APX, c), glutathione reductase (GR, d), guaiacol peroxidase (POX, e) and polyphenol oxidase (PPO, f) activity in maize leaf 8 grown under optimal control conditions (C), subjected to mite infestation (Tu+), soil drought (D+) and both stresses (Tu + D) simultaneously, and in noninfested leaf 9 (Tu−) in the immediate vicinity of mite-infested leaf 8 and respective control (C). Different letters above bars indicate statistically significant differences at the significance level 0.05 (a, b, c, f—HSD Tukey test; d, e—Kruskal–Wallis test)

Fig. 2

a–b Total protein content (a) and the concentration of derivatized carbonyl groups of oxidized proteins (b) in maize leaf 8 grown under optimal control conditions (C), subjected to mite infestation (Tu+), soil drought (D+) and both stresses (Tu + D) simultaneously, and in noninfested leaf 9 (Tu−) in the immediate vicinity of mite-infested leaf 8 and respective control (C). Different letters above bars indicate statistically significant differences at the significance level 0.05 (Kruskal–Wallis test)

Fig. 3

a–d Representative 2-DE gels of CBB-stained proteins extracted from mite-infested leaf 8 (a), soil drought-treated (b), double-stressed (c), and from noninfested leaf 9 close to the mite-infested leaf 8 (d). Within each gel, numbers indicating protein spots differentiating treatment and unstressed control correspond to those in Table 2 and 3. In the first dimension, IPG strips (Bio-Rad Laboratories, USA) of pH 4–7 (indicating pI) were used to separate proteins. In the second dimension, 11 % polyacrylamide gel was used. Standard molecular masses (kDa) are indicated

Fig. 4

a–f Representative mean images with marked significant spots differentiating the classes—C(8) and [Tu + (8)] (a), C(8) and [D + (8)] (b) and C(8) and [Tu + D(8)] (c). Below, mean images presenting the spots shared by mite [Tu + (8)] and drought [D + (8)] stresses (marked green; d and e), by drought [D + (8)] and double stresses [Tu + D(8)] (marked red; e and f) and by mite [Tu + (8)] and double stresses [Tu + D(8)] (marked blue; d and f)

Fig. 5

a–c Representative mean images with marked significant spots differentiating classes C(8) and C(9) (a), C(9) and Tu − (9) (b), Tu + (8) and Tu − (9) (c)

Fig. 6

a–d The results from PCA of 24 samples obtained from four classes C(8), Tu + (8), Tu + D(8) and D + (8) presented in the form of score (a, b) and loading plots (c, d) onto the planes defined by PC1 and PC2, and PC1 and PC3, respectively

Fig. 7

a–d The results from PCA of 36 samples obtained from six classes C(8), Tu + (8), Tu + D(8), D + (8), C(9) and Tu − (9) presented in form of score (a, b) and loading plots (c, d) onto the planes defined by PC1 and PC2, and PC1 and PC3, respectively

Fig. 8

Dendrograms for 24 samples obtained from four classes [C(8), Tu + (8), Tu + D(8), D + (8)] augmented with the heat map of centred data matrix (with columns and rows sorted out in the corresponding dendrograms). Gradations of colour from dark blue to red in the colour bar indicate the increase in value of data elements

Fig. 9

Dendrograms for 36 samples obtained from six classes [C(8), Tu + (8), Tu + D(8), D + (8), C(9), Tu − (9)] augmented with the heat map of centred data matrix (with columns and rows sorted out in the corresponding dendrograms). Gradations of colour from dark blue to red in the colour bar indicate the increase in value of data elements

Fig. 10

Venn diagrams showing the overlapping of increased (a) or decreased (b) abundance of maize leaf proteins upon mite infestation [Tu + (8)], soil drought [(D + (8)] and a combination of stresses [Tu + D(8)]