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Main conclusion 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. Electronic supplementary material The online version of this article (doi:10.1007/s00425-016-2559-6) contains supplementary material, which is available to authorized users.

Ranunculus asiaticus' is a horticultural dicot that is able to tolerate long-term desiccation during its annual life cycle. The annual cycle of desiccation and resurrection of 'R. asiaticus' is correlated with the presence of a putative storage protein (Ra14) and stress-related proteins (dehydrins and smHSPs) in its underground storage organs, the tuberous roots. The 14 kDa protein (Ra14) as a major root protein fluctuates seasonally and increases upon drying. It is a glycoprotein and has an amphipathic character. A 492 bp full-length Ra14 cDNA sequence and a 615 bp genomic sequence were obtained by 3'-RACE and 5'-RACE PCR using oligonucleotide sequences based on the terminal amino acids of the 14 kDa mature protein. A 500 bp probe based on the Ra14 genomic sequence detected at least 4 homologs in 'R. asiaticus ' using Southern blots. The 14 kDa protein was localized in the storage vacuoles in 'R. asiaticus' roots using an antibody raised against it. SDS-PAGE analysis of total proteins extracted from different organs of ' R. asiaticus' revealed that the 14 kDa protein is specifically expressed and synthesized in tuberous roots but not in above-ground vegetative organs such as leaves and stems, and its homolog was only detected in 'Anemone ' corms, a desiccation-tolerant organ. Immunoblots indicated that dehydrins (LEAII D-11 family) are present in desiccated roots and their expression declined upon rehydration. A 477 bp full-length cDNA sequence of Dhn17.5 encoding a 17.5 kDa dehydrin and a 543 bp full-length cDNA sequence of Dhn20 encoding a 20 kDa dehydrin were obtained by degenerate PCR, 3'-RACE and 5'-RACE PCR. The expression of Dhn20 was induced by dehydration and ABA but not by salt. As with dehydrins, smHSPs were also detected by immunoblots in the tuberous roots during desiccation, and their expression was induced by dehydration, ABA and salt. Gel filtration chromatography showed that smHSPs may act as molecular chaperons which are able to bind to other molecules during desiccation to protect them from damage. A possible interaction between the 14 kDa protein and smHSPs was determined using S-tagged 14 kDa protein and total proteins extracted from desiccated roots, but the gel filtration chromatography showed that there is no interaction between the two 'in vivo'.

Ten proteins differentially regulated by progressive drought stress in Arabidopsis Columbia wild-type, axr1-3 and axr2-1auxin-insensitive mutants, were identified from internal amino acid microsequencing. These proteins fell into two categories: (i) stress-related proteins, known to be induced by rapid water stress via abscisic acid (ABA)-dependent or -independent pathways [late embryogenesis abundant (LEA)-like and heat shock cognate (HS) 70, respectively], or in response to pathogens or oxidative stress [β-1,3 glucanase (BG), annexin] and (ii) metabolic enzymes [glutamine synthetase (GS), fructokinase (Frk), caffeoyl-CoA-3-O-methyltransferase (CCoAOMT)]. The differential behaviour of these proteins highlighted a role for AXR2 and/or AXR1 in the regulation of their abundance during drought adaptation. In particular, reduced induction of RD29B, GS and annexin, and overexpression of BG2 were observed specifically in the axr1-3 mutant, which is dramatically affected in several ABA-dependent drought adaptive responses, such as drought rhizogenesis. Altogether these results indicate cross-talk between auxin- and ABA-signalling in Arabidopsis drought responses.