Table 6. Effects of K deficiency on the contents of the classified proteins in the cotton xylem sap with ≥ 2- or ≤ 0.5-fold change in comparison between LK and NK and on proteins lacking in either the LK or NK treatment.
| Classification | Accession No. | Protein name | Plant species | Theoretical MW/pI | Secrete traits | FC |
|---|---|---|---|---|---|---|
| PR-1 | A0A061DWT3 | Basic pathogenesis-related protein 1 | Theobroma cacao | 24.2/4.85 | NCSP | 0.21** |
| 1,3-beta-glucosidase | E7CQZ9 | GLU | Gossypium hirsutum | 50.3/5.15 | CSP | 0.44* |
| B9RKF7 | Glucan endo-1,3-beta-glucosidase, putative | Ricinus communis | 55.7/6.40 | CSP | 0.18** | |
| A0A061GR43 | O-Glycosyl hydrolases family 17 protein isoform 1 | Theobroma cacao | 53.1/4.98 | NCSP | 0.32** | |
| P93153 | 1,3-beta-glucanase | Gossypium hirsutum | 37.6/5.03 | CSP | NLK | |
| A0A061GVZ6 | O-Glycosyl hydrolases family 17 protein isoform 1 | Theobroma cacao | 53.7/8.01 | NLK | ||
| Chitinase | A0A061G8M3 | Acidic endochitinase | Theobroma cacao | 36.1/9.87 | NCSP | 0.11** |
| D7RTU7 | Class I chitinase | Gossypium hirsutum | 34.7/6.66 | CSP | 0.21*** | |
| P93154 | Chitinase ` | Gossypium hirsutum | 28.8/6.25 | CSP | 0.27*** | |
| E5FQ62 | Class 3 chitinase | Hippophae rhamnoides | 31.8/9.05 | CSP | NLK | |
| L7NJI5 | Class IV chitinase | Gossypium barbadense | 28.6/4.85 | CSP | NLK | |
| PR-5 | Q2HPG3 | Osmotin-like protein I | Gossypium hirsutum | 26.5/7.68 | CSP | 0.07* |
| Protease inhibitor | A0A061EZK2 | Kunitz family trypsin and protease inhibitor protein | Theobroma cacao | 21.5/6.47 | CSP | 0.22* |
| I7GGD4 | Proteinase inhibitor | Gossypium arboreum | 7.5/4.95 | NCSP | 7.15*** | |
| Q6WMU5 | Polygalacturonase-inhibiting protein | Gossypium barbadense | 37.1/8.32 | CSP | 0.38** | |
| Proteases | V4TEG7 | Carboxypeptidase (serine-type) | Citrus clementina | 54.0/4.99 | CSP | 0.11** |
| G7IU18 | Subtilisin-like serine protease | Medicago truncatula | 81.9/7.88 | CSP | 0.35** | |
| B9RNR8 | Aspartic proteinase nepenthesin-2, putative | Ricinus communis | 48.8/8.19 | CSP | 0.15*** | |
| A0A061E9G1 | Xylem cysteine peptidase 1 | Theobroma cacao | 39.1/5.66 | NCSP | 0.20*** | |
| A0A061GL56 | Cysteine proteinases superfamily protein | Theobroma cacao | 39.0/5.40 | CSP | 0.24** | |
| Peroxidases | A0A061ET17 | Peroxidase superfamily protein | Theobroma cacao | 37.4/6.50 | CSP | 0.06*** |
| V9PBI4 | POD21 | Populus tomentosa | 37.8/6.66 | CSP | 0.06** | |
| Q570F0 | Peroxidase ATP4a (Fragment) | Arabidopsis thaliana | 24.6/4.45 | NCSP | 0.10** | |
| Q8RVP3 | Apoplastic anionic gaiacol peroxidase | Gossypium hirsutum | 37.4/4.60 | CSP | 0.11*** | |
| A0A067JYQ4 | Peroxidase | Jatropha curcas | 36.2/5.22 | CSP | 0.11*** | |
| Q6UNK7 | POD9 | Gossypium hirsutum | 34.9/7.75 | CSP | 0.11*** | |
| A0A061DQ02 | Peroxidase superfamily protein | Theobroma cacao | 35.6/4.95 | CSP | 0.12* | |
| G7KFM2 | Class III peroxidase | Medicago truncatula | 35.8/9.81 | CSP | 0.13*** | |
| A0A058ZQS8 | Peroxidase | Eucalyptus grandis | 35.5/8.32 | CSP | 0.15*** | |
| Q4W1I8 | Basic peroxidase | Zinnia violacea | 34.2/8.32 | CSP | 0.16*** | |
| Q7XYR7 | Class III peroxidase | Gossypium hirsutum | 35.4/9.40 | CSP | 0.3** | |
| C6TF32 | Peroxidase | Glycine max | 34.5/9.14 | CSP | 0.33*** | |
| C9WF04 | Class III peroxidase | Gossypium hirsutum | 35.3/7.68 | CSP | 0.35* | |
| C9WF05 | Class III peroxidase | Gossypium hirsutum | 34.0/8.33 | CSP | 0.40* | |
| A0A061E3B2 | Cationic peroxidase 2 | Theobroma cacao | 39.7/7.47 | NCSP | 0.44*** | |
| M5WMM3 | Peroxidase | Prunus persica | 35.7/7.29 | CSP | 2.65*** | |
| A0A059AII4 | Peroxidase | Eucalyptus grandis | 33.9/8.92 | CSP | NLK | |
| A0A061DGV9 | Peroxidase superfamily protein | Theobroma cacao | 36.8/9.54 | CSP | NLK | |
| B9MXK6 | Class III peroxidase | Populus trichocarpa | 36.4/9.69 | CSP | NLK | |
| B3SRB5 | Putative secretory peroxidase | Catharanthus roseus | 35.3/9.10 | CSP | NLK | |
| G7JMV9 | Peroxidase family protein | Medicago truncatula | 37.6/9.34 | CSP | NLK | |
| G7INU9 | Cationic peroxidase | Medicago truncatula | 34.7/7.70 | CSP | NLK | |
| B9SXK5 | Peroxidase 53, putative | Ricinus communis | 35.1/46.3 | CSP | NLK | |
| A0A061ENE1 | Peroxidase 24, putative | Theobroma cacao | 36.4/9.71 | CSP | NLK | |
| M1JUJ2 | Peroxidase 2 | Pyrus communis | 34.5/9.99 | CSP | NLK | |
| D4NYQ9 | Peroxidase | Bruguiera | 36.4/10.37 | CSP | NLK | |
| X5GE19 | Peroxidase | Carica papaya | 37.9/6.73 | CSP | NLK | |
| Lipid-transfer protein | Q9M6B6 | Non-specific lipid-transfer protein | Gossypium hirsutum | 11.9/8.72 | CSP | 2.43** |
| Oxido-reduction- related proteins | F4YAW2 | Copper binding protein 3 | Gossypium hirsutum | 17.8/4.30 | CSP | 0.33* |
| A0A061ECX6 | Cupredoxin superfamily protein | Theobroma cacao | 22.2/7.97 | NCSP | 0.48* | |
| A0A067F2G2 | Superoxide dismutase [Cu-Zn] | Citrus sinensis | 28.9/7.22 | CSP | 2.00** | |
| Q6TDS6 | Laccase | Gossypium arboreum | 63.3/6.73. | CSP | NLK | |
| A0A078DZJ6 | BnaC07g17890D protein (UDP-N-acetylmuramate dehydrogenase activity) | Brassica napus | 61.0/7.99 | CSP | NLK | |
| Signaling proteins | A9XTL5 | Fasciclin-like arabinogalactan protein 10 | Gossypium hirsutum | 44.3/6.73 | CSP | NLK |
| A9XTL7 | Fasciclin-like arabinogalactan protein 12 | Gossypium hirsutum | 42.9/5.34 | CSP | 0.15*** | |
| A0A061GBZ8 | Receptor-like protein kinase-related family protein | Theobroma cacao | 26.7/6.47 | CSP | 0.49* | |
| A0A061EHM2 | NSP-interacting kinase 1 | Theobroma cacao | 71.6/8.04 | CSP | NLK | |
| A0A061GG78 | Cysteine-rich RLK 29 (protein serine/threonine kinase activity) | Theobroma cacao | 149.6/5.32 | CSP | NLK | |
| G7J0F7 | Lorelei-like-GPI-anchored protein | Medicago truncatula G | 18.6/5.61 | CSP | NLK | |
| B2ZAQ1 | Peptidoglycan-binding LysM domain-containing related protein | Gossypioides kirkii | 47.3/5.30 | CSP | NLK | |
| Other stress-related proteins | B9RP09 | Heparanase, putative | Ricinus communis | 57.3/7.49 | NCSP | NLK |
| I3T0C3 | Histone H4 | Medicago truncatula | 11.4/12.01 | 7.54** | ||
| W9RXK9 | Histone H2A | Morus notabilis | 47.3/10.69 | NCSP | NNK | |
| Cell wall metabolism | A0A061GPN5 | Xyloglucan endotransglucosylase/hydrolase (GH16) | Theobroma cacao | 33.3/6.92 | CSP | 0.21*** |
| V4WIU8 | Xyloglucan endotransglucosylase/hydrolase (GH16) | Citrus clementina | 31.1/8.68 | NCSP | NLK | |
| B9RN80 | Polygalacturonase, putative (GH28) | Ricinus communis | 59.0/5.58 | CSP | NLK | |
| W9RBM9 | Beta-fructofuranosidase, insoluble isoenzyme CWINV1 | Morus notabilis | 72.5/5.96 | NCSP | 0.40* | |
| A0A061EW87 | Alpha-L-arabinofuranosidase 1 | Theobroma cacao | 75.5/4.70 | CSP | NLK | |
| A0A061EP57 | Glycosyl hydrolase superfamily protein isoform 3 (GH1) | Theobroma cacao | 66.0/6.60 | NLK | ||
| G7IRQ2 | Beta-galactosidase (GH35) | Medicago truncatula | 91.4/7.58 | CSP | NLK | |
| A0A078IVA9 | Beta-galactosidase (GH35) | Brassica napus | 114.1/7.38 | NCSP | NLK | |
| W9SX00 | Putative beta-D-xylosidase 5 | Morus notabilis | 87.0/5.98 | CSP | NLK | |
| Q76MS5 | LEXYL1 protein(hydrolyzing O-glycosyl) | Solanum lycopersicum | 83.1/7.89 | CSP | NLK | |
| A0A068TXE7 | Coffea canephora DH200 = 94 genomic scaffold, scaffold_6 (hydrolyzing O-glycosyl compounds) | Coffea canephora | 106.4/6.24 | NCSP | 2.40** | |
| Proteins with interacting domains | A0A061FFL8 | Curculin-like (Mannose-binding) lectin family protein | Theobroma cacao | 51.3/8.17 | CSP | 0.09* |
| A0A061F8Q5 | D-mannose binding lectin protein with Apple-like carbohydrate-binding domain, putative | Theobroma cacao | 49.0/8.27 | CSP | 0.13** | |
| Miscellaneous proteins | F4HR91 | Leucine-rich repeat (LRR) family protein | Arabidopsis thaliana | 52.7/8.67 | CSP | 0.05*** |
| I0B675 | Epidermis-specific secreted glycoprotein EP1-like protein | Gossypium hirsutum | 49.0/6.75 | CSP | 0.17** |
Note: LK: low K; NK: normal K; NLK: being non-detectable in LK; NNK: being non-detectable in NK; FC: fold change; CSP: classical secreted proteins; NCSP: non-classical secreted proteins; *P ≤ 0.05; **P ≤ 0.01; ***: P ≤ 0.001