The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The target is Zea mays (maize) Endochitinase B, UniProt accession P29023, also called ChitB / seed chitinase B, gene name CHIB (synonym CTB1). In maize genomic resources and the primary experimental literature retrieved here, “chitinase B / ChiB / ChitB” corresponds to gene model GRMZM2G005633, annotated as a GH19 plant chitinase and class IV endochitinase, matching the UniProt description (GH19 family; precursor/secreted). (han2021maizeendochitinaseexpressiona pages 5-6, han2021maizeendochitinaseexpression media 094c2120)
CHIB (P29023) encodes a plant endochitinase (EC 3.2.1.14) in glycoside hydrolase family 19 (GH19). GH19 chitinases are generally described as endo-acting enzymes that hydrolyze β-1,4 glycosidic linkages in chitin (a linear polymer of N-acetylglucosamine, GlcNAc), a key structural component of fungal cell walls and arthropod exoskeletons. (han2021maizeendochitinaseexpressiona pages 1-3, ubhayasekera2011structureandfunction pages 1-2)
A central mechanistic feature of GH19 chitinases is a single-step inverting mechanism (i.e., inversion of anomeric configuration during hydrolysis). The catalytic site lies in a wide cleft within a highly α-helical, bilobed protein fold; catalysis is associated with conserved glutamate residues separated by distances typical of inverting glycosidases. (ubhayasekera2011structureandfunction pages 3-5, ubhayasekera2011structureandfunction pages 6-7)
Plant GH19 chitinases are commonly grouped into classes (I–VI in some schemes). Class differences are associated with domain composition and loop architecture bordering the active-site cleft:
- Class I vs II: broadly similar, but class I typically includes an N-terminal chitin-binding module (CtBM/CBD) that can enhance activity on insoluble chitin and contribute to antifungal effectiveness. (ubhayasekera2011structureandfunction pages 1-2, ubhayasekera2011structureandfunction pages 5-6)
- Class IV: compared to class I/II, class IV enzymes can show loop deletions and are described in one maize-focused study as containing a CBD but lacking a particular C-terminal extension (CTE) in that class definition. (han2021maizeendochitinaseexpressiona pages 3-4, ubhayasekera2011structureandfunction pages 5-6)
In maize, CHIB/ChiB is classified as a class IV GH19 chitinase and is predicted to contain both a signal peptide and a chitin-binding domain (CBD) plus the catalytic domain. (han2021maizeendochitinaseexpressiona pages 5-6, han2021maizeendochitinaseexpression media 094c2120)
A key experimentally grounded annotation from maize is that ChiB/CHIB is predicted to contain:
- Signal peptide (SP) → consistent with secretion and extracellular/apoplastic deployment
- Chitin-binding domain (CBD; cd00035)
- Catalytic domain (cd00325)
- Length in multiple maize inbreds around 281–282 aa, with predicted mature protein mass around ~29 kDa. (han2021maizeendochitinaseexpressiona pages 5-6, han2021maizeendochitinaseexpression media 094c2120)
These properties support the functional model that CHIB is synthesized as a precursor that is directed into the secretory pathway, and likely functions in the apoplast/extracellular space (including seed extracellular matrices), where it can encounter chitin-containing microbes or chitinous insect structures.
Direct CHIB-specific kinetic constants were not available in the retrieved CHIB-specific evidence. However, CHIB’s assignment to EC 3.2.1.14 and GH19 strongly supports that its primary biochemical function is endo-hydrolysis of β-1,4 linkages in chitin, producing chitooligosaccharides. (han2021maizeendochitinaseexpressiona pages 1-3, ubhayasekera2011structureandfunction pages 1-2)
A maize primary study investigating insect herbivory identified ChiB/CHIB as one of four cloned maize chitinase genes and reports that transcript abundance increases dramatically in response to mechanical wounding and fall armyworm (Spodoptera frugiperda) feeding. In that dataset, the fold-change induction of ChiB was generally ~10-fold (and similar magnitude to ChiI), with genotype-dependent basal expression (higher basal ChiB expression in Mp708 than Tx601). (han2021maizeendochitinaseexpressiona pages 6-7)
This supports CHIB’s placement within plant defense signaling frameworks in which physical damage and herbivore-associated cues activate defense gene expression.
In the same maize study, a compiled organ/development expression annotation indicates that ChiB has highest expression in seed among surveyed organs (as presented in their Table annotation). (han2021maizeendochitinaseexpressiona pages 5-6, han2021maizeendochitinaseexpression media 094c2120)
Although the enzymatic activity assays used in the maize study could not discriminate among individual chitinase isoforms, the authors detected chitinase activity in fall armyworm food bolus and frass, indicating that plant chitinases can remain active after ingestion and transit through the insect gut environment—supporting plausibility of direct anti-insect action by chitinases against chitin-containing structures (e.g., peritrophic matrix). (han2021maizeendochitinaseexpressiona pages 6-7)
ChiB maps to chromosome 10 and co-localizes with insect resistance QTL regions reported for fall armyworm and southwestern corn borer (as summarized in the maize study’s annotation). While this does not prove causality, it is consistent with CHIB being a plausible contributor to quantitative resistance. (han2021maizeendochitinaseexpressiona pages 5-6)
A 2024 study/review focusing on root-associated chitinases performed modeling and mutagenesis on a different maize GH19 chitinase (ZmChi19A), confirming key catalytic residues and domain requirements for activity against insoluble substrates and fungi. Key quantitative findings include:
- Apparent Km ~30 µM for the soluble substrate 4-MU-GlcNAc3 (for ZmChi19A). (shobade2024plantrootassociated pages 8-9)
- Activity optima: ZmChi19A activity described as optimal across pH 7–9 and 50–60°C (with one excerpt specifying pH 8 and 50°C). (shobade2024plantrootassociated pages 1-2, shobade2024plantrootassociated pages 6-8)
- Catalytic residues validated by mutagenesis: Glu147 and Glu169 are essential for activity. (shobade2024plantrootassociated pages 8-9, shobade2024plantrootassociated pages 6-8)
Although this is not CHIB, it provides a 2024 experimentally grounded biochemical reference point for how maize GH19 enzymes achieve chitin hydrolysis and antifungal effects, and underscores the functional importance of CBD-associated interactions with insoluble chitinous surfaces—relevant for interpreting CHIB’s predicted SP + CBD architecture. (shobade2024plantrootassociated pages 8-9, shobade2024plantrootassociated pages 6-8)
A 2024 broad review emphasizes chitinases as candidate biopesticides/biocontrol agents and as tools for sustainability (e.g., valorizing chitin-rich waste), while highlighting risks such as non-target effects and dual-use concerns. It also provides quantitative global context on chitin availability and waste. (unuofin2024chitinasesexpandingthe pages 1-2, unuofin2024chitinasesexpandingthe pages 12-13)
A 2024 applied study (not maize CHIB; instead bacterial Serratia marcescens ChiB, GH18) illustrates current translational implementation of chitinase biology for maize pest control. Key data:
- Source strain showed 250 U/mg chitinase activity; recombinant expression increased production 2.5-fold. (elsayed2024genecloningheterologous pages 1-2)
- In laboratory assays against Spodoptera frugiperda, reported mortality 92.75 ± 0.17% vs control 8 ± 0.14% (positive chemical control emamectin benzoate: 98.31 ± 0.28%). (elsayed2024genecloningheterologous pages 11-13)
- Field trial implementation details: crude enzyme solution 2000 U/mL, applied 10 mL per plant (knapsack sprayer), with repeated application. (elsayed2024genecloningheterologous pages 21-22)
- Field outcomes included reductions in larval pupation of 75% at 7 days and 88.66% at 10 days post-treatment (emamectin: 86% and 91.3%). (elsayed2024genecloningheterologous pages 11-13)
This does not functionally annotate maize CHIB, but it demonstrates that chitinases are being evaluated in controlled field conditions on maize with measurable efficacy, supporting the relevance of plant chitinases (including CHIB) as part of broader chitinase-enabled integrated pest management concepts. (elsayed2024genecloningheterologous pages 11-13, elsayed2024genecloningheterologous pages 21-22)
The maize herbivory study provides a mechanistic implementation concept on the plant side: CHIB expression is inducible (~10-fold) under insect feeding and wounding, and chitinase activity can persist through insect digestion. This supports the premise that endogenous plant chitinases (including CHIB) could contribute to resistance traits and/or be leveraged in breeding/engineering approaches, even though direct CHIB efficacy assays were not retrieved here. (han2021maizeendochitinaseexpressiona pages 6-7)
The GH19 structural review emphasizes that GH19 enzymes use a wide cleft in an α-helical bilobed fold and that loop architecture and presence/absence of chitin-binding modules can modulate substrate engagement—particularly for insoluble chitin—which is often the biologically relevant form in fungal cell walls. This supports the interpretation that CHIB’s predicted CBD likely improves performance against insoluble chitinous substrates and contributes to defense effectiveness. (ubhayasekera2011structureandfunction pages 5-6, ubhayasekera2011structureandfunction pages 2-3)
The GH19 review discusses extracellular targeting trends for some classes (including class IV in the excerpt) associated with absence of specific C-terminal features, and the maize CHIB prediction includes a signal peptide, consistent with secretion to sites of pathogen/insect interface. (ubhayasekera2011structureandfunction pages 2-3, han2021maizeendochitinaseexpressiona pages 5-6)
The 2024 broad review frames chitinases as promising for sustainable agriculture and waste valorization, but explicitly raises concerns about ecological impact, resistance evolution, and governance/dual-use risks, recommending careful consideration when deploying chitinase technologies. (unuofin2024chitinasesexpandingthe pages 12-13)
| Gene/protein | Names / identifiers | Enzyme class | Predicted domains / architecture | Approx. length / mass | Likely localization | Inducing conditions / expression context | Recent biochemical examples / notes | Key supporting citations |
|---|---|---|---|---|---|---|---|---|
| CHIB (target gene) | Endochitinase B; ChitB; seed chitinase B; UniProt P29023; gene model GRMZM2G005633 | EC 3.2.1.14; glycoside hydrolase family 19 (GH19); class IV plant endochitinase | Signal peptide present; chitin-binding domain (CBD; cd00035) present; catalytic domain (cd00325) present; class IV GH19 architecture | ~281–282 aa; predicted mature protein ~29 kDa | Likely secreted / apoplastic or extracellular, consistent with signal peptide and seed/pathogenesis-related chitinase annotation | Transcript abundance and total chitinase activity increase after mechanical wounding and fall armyworm herbivory; high organ expression reported in seed; Table 1 image supports SP/CBD/domain assignment | Direct CHIB-specific kinetic constants were not provided in the retrieved excerpts; function is inferred as an endochitinase that hydrolyzes β-1,4 linkages in chitin, consistent with GH19 catalytic mechanism | (han2021maizeendochitinaseexpressiona pages 5-6, han2021maizeendochitinaseexpressiona pages 3-4, han2021maizeendochitinaseexpressiona pages 1-3, han2021maizeendochitinaseexpression media 094c2120) |
| ZmChi19A (comparison only; different maize GH19 gene, not CHIB) | Zea mays basic endochitinase; root-associated GH19 chitinase | GH19; class I endochitinase | N-terminal hevein-like CBD; α-helical catalytic domain; flexible C-terminal domain; catalytic residues E147 and E169 | Not summarized in retrieved excerpt | Root-secreted / rhizosphere-associated | Studied as a root-associated defense enzyme; antifungal activity against Aspergillus niger | Apparent Km ~30 µM for 4-MU-GlcNAc3; optimum around pH 7–9 and 50–60°C (more specifically pH 8 and 50°C in one excerpt); CBD and flexible C-terminal domain are required for efficient colloidal chitin cleavage and fungal growth inhibition | (shobade2024plantrootassociated pages 8-9, shobade2024plantrootassociated pages 6-8, shobade2024plantrootassociated pages 1-2, shobade2024plantrootassociated pages 4-6) |
Table: This table summarizes the core functional annotation for the maize CHIB/ChitB protein targeted in the report, using evidence that specifically matches UniProt P29023 and the maize gene model GRMZM2G005633. It also includes a clearly separated comparison row for a different maize GH19 chitinase, ZmChi19A, to illustrate recent biochemical parameters available for related GH19 enzymes.
In addition, the following visual evidence directly supports CHIB’s predicted domain/class assignment in maize (Table 1 from Han et al. 2021): (han2021maizeendochitinaseexpression media 094c2120)
References
(han2021maizeendochitinaseexpressiona pages 5-6): Yang Han, Erin B. Taylor, and Dawn Luthe. Maize endochitinase expression in response to fall armyworm herbivory. May 2021. URL: https://doi.org/10.1007/s10886-021-01284-9, doi:10.1007/s10886-021-01284-9. This article has 18 citations and is from a peer-reviewed journal.
(han2021maizeendochitinaseexpression media 094c2120): Yang Han, Erin B. Taylor, and Dawn Luthe. Maize endochitinase expression in response to fall armyworm herbivory. May 2021. URL: https://doi.org/10.1007/s10886-021-01284-9, doi:10.1007/s10886-021-01284-9. This article has 18 citations and is from a peer-reviewed journal.
(han2021maizeendochitinaseexpressiona pages 1-3): Yang Han, Erin B. Taylor, and Dawn Luthe. Maize endochitinase expression in response to fall armyworm herbivory. May 2021. URL: https://doi.org/10.1007/s10886-021-01284-9, doi:10.1007/s10886-021-01284-9. This article has 18 citations and is from a peer-reviewed journal.
(ubhayasekera2011structureandfunction pages 1-2): Wimal Ubhayasekera. Structure and function of chitinases from glycoside hydrolase family 19. Polymer International, 60:890-896, Jun 2011. URL: https://doi.org/10.1002/pi.3028, doi:10.1002/pi.3028. This article has 44 citations and is from a peer-reviewed journal.
(ubhayasekera2011structureandfunction pages 3-5): Wimal Ubhayasekera. Structure and function of chitinases from glycoside hydrolase family 19. Polymer International, 60:890-896, Jun 2011. URL: https://doi.org/10.1002/pi.3028, doi:10.1002/pi.3028. This article has 44 citations and is from a peer-reviewed journal.
(ubhayasekera2011structureandfunction pages 6-7): Wimal Ubhayasekera. Structure and function of chitinases from glycoside hydrolase family 19. Polymer International, 60:890-896, Jun 2011. URL: https://doi.org/10.1002/pi.3028, doi:10.1002/pi.3028. This article has 44 citations and is from a peer-reviewed journal.
(ubhayasekera2011structureandfunction pages 5-6): Wimal Ubhayasekera. Structure and function of chitinases from glycoside hydrolase family 19. Polymer International, 60:890-896, Jun 2011. URL: https://doi.org/10.1002/pi.3028, doi:10.1002/pi.3028. This article has 44 citations and is from a peer-reviewed journal.
(han2021maizeendochitinaseexpressiona pages 3-4): Yang Han, Erin B. Taylor, and Dawn Luthe. Maize endochitinase expression in response to fall armyworm herbivory. May 2021. URL: https://doi.org/10.1007/s10886-021-01284-9, doi:10.1007/s10886-021-01284-9. This article has 18 citations and is from a peer-reviewed journal.
(han2021maizeendochitinaseexpressiona pages 6-7): Yang Han, Erin B. Taylor, and Dawn Luthe. Maize endochitinase expression in response to fall armyworm herbivory. May 2021. URL: https://doi.org/10.1007/s10886-021-01284-9, doi:10.1007/s10886-021-01284-9. This article has 18 citations and is from a peer-reviewed journal.
(shobade2024plantrootassociated pages 8-9): Samuel O. Shobade, Olga A. Zabotina, and Marit Nilsen-Hamilton. Plant root associated chitinases: structures and functions. Frontiers in Plant Science, Feb 2024. URL: https://doi.org/10.3389/fpls.2024.1344142, doi:10.3389/fpls.2024.1344142. This article has 28 citations.
(shobade2024plantrootassociated pages 1-2): Samuel O. Shobade, Olga A. Zabotina, and Marit Nilsen-Hamilton. Plant root associated chitinases: structures and functions. Frontiers in Plant Science, Feb 2024. URL: https://doi.org/10.3389/fpls.2024.1344142, doi:10.3389/fpls.2024.1344142. This article has 28 citations.
(shobade2024plantrootassociated pages 6-8): Samuel O. Shobade, Olga A. Zabotina, and Marit Nilsen-Hamilton. Plant root associated chitinases: structures and functions. Frontiers in Plant Science, Feb 2024. URL: https://doi.org/10.3389/fpls.2024.1344142, doi:10.3389/fpls.2024.1344142. This article has 28 citations.
(unuofin2024chitinasesexpandingthe pages 1-2): John Onolame Unuofin, Olubusola Ayoola Odeniyi, Omolara Sola Majengbasan, Aboi Igwaran, Karabelo MacMillan Moloantoa, Zenzile Peter Khetsha, Samuel Ayodele Iwarere, and Michael Olawale Daramola. Chitinases: expanding the boundaries of knowledge beyond routinized chitin degradation. Environmental Science and Pollution Research International, 31:38045-38060, May 2024. URL: https://doi.org/10.1007/s11356-024-33728-6, doi:10.1007/s11356-024-33728-6. This article has 54 citations.
(unuofin2024chitinasesexpandingthe pages 12-13): John Onolame Unuofin, Olubusola Ayoola Odeniyi, Omolara Sola Majengbasan, Aboi Igwaran, Karabelo MacMillan Moloantoa, Zenzile Peter Khetsha, Samuel Ayodele Iwarere, and Michael Olawale Daramola. Chitinases: expanding the boundaries of knowledge beyond routinized chitin degradation. Environmental Science and Pollution Research International, 31:38045-38060, May 2024. URL: https://doi.org/10.1007/s11356-024-33728-6, doi:10.1007/s11356-024-33728-6. This article has 54 citations.
(elsayed2024genecloningheterologous pages 1-2): Ghada M. El-Sayed, Maha T. H. Emam, Maher A. Hammad, and Shaymaa H. Mahmoud. Gene cloning, heterologous expression, and in silico analysis of chitinase b from serratia marcescens for biocontrol of spodoptera frugiperda larvae infesting maize crops. Molecules, 29:1466, Mar 2024. URL: https://doi.org/10.3390/molecules29071466, doi:10.3390/molecules29071466. This article has 19 citations.
(elsayed2024genecloningheterologous pages 11-13): Ghada M. El-Sayed, Maha T. H. Emam, Maher A. Hammad, and Shaymaa H. Mahmoud. Gene cloning, heterologous expression, and in silico analysis of chitinase b from serratia marcescens for biocontrol of spodoptera frugiperda larvae infesting maize crops. Molecules, 29:1466, Mar 2024. URL: https://doi.org/10.3390/molecules29071466, doi:10.3390/molecules29071466. This article has 19 citations.
(elsayed2024genecloningheterologous pages 21-22): Ghada M. El-Sayed, Maha T. H. Emam, Maher A. Hammad, and Shaymaa H. Mahmoud. Gene cloning, heterologous expression, and in silico analysis of chitinase b from serratia marcescens for biocontrol of spodoptera frugiperda larvae infesting maize crops. Molecules, 29:1466, Mar 2024. URL: https://doi.org/10.3390/molecules29071466, doi:10.3390/molecules29071466. This article has 19 citations.
(ubhayasekera2011structureandfunction pages 2-3): Wimal Ubhayasekera. Structure and function of chitinases from glycoside hydrolase family 19. Polymer International, 60:890-896, Jun 2011. URL: https://doi.org/10.1002/pi.3028, doi:10.1002/pi.3028. This article has 44 citations and is from a peer-reviewed journal.
(shobade2024plantrootassociated pages 4-6): Samuel O. Shobade, Olga A. Zabotina, and Marit Nilsen-Hamilton. Plant root associated chitinases: structures and functions. Frontiers in Plant Science, Feb 2024. URL: https://doi.org/10.3389/fpls.2024.1344142, doi:10.3389/fpls.2024.1344142. This article has 28 citations.