Insights into the molecular control of cross-incompatibility in Zea mays

Authors: LU, YONGXIAN - Carnegie Institute - Washington; Moran Lauter, Adrienne; MAKKENA, SRILAKSHMI - Indiana Crop Improvement Association (ICIA); Scott, Marvin; EVANS, MATTHEW - Carnegie Institute - Washington

Submitted to: Plant Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2020
Publication Date: 8/31/2020
Citation: Lu, Y., Moran Lauter, A., Makkena, S., Scott, M.P., Evans, M.M. 2020. Insights into the molecular control of cross-incompatibility in Zea mays. Plant Reproduction. 33: 117-128. https://doi.org/10.1007/s00497-020-00394-w.
DOI: https://doi.org/10.1007/s00497-020-00394-w

Interpretive Summary: Pollen grains landing on the silks of corn precedes fertilization and eventually leads to the production of grain that is harvested for food, feed or fuel, or planting. While most corn plants can freely fertilize each other, some cannot due to heritable cross incompatibility systems. The ability to control which plants fertilize each other is extremely valuable for preserving the genetic purity of different corn varieties. This manuscript presents a review of recent information about cross incompatibility systems in corn and presents a molecular model for how such systems may function. This information will be valuable to scientists who study male-female interactions that lead to fertilization by providing testable hypotheses about how the cross incompatibility systems work.

Technical Abstract: Gametophytic cross incompatibly systems in corn have been the subject of genetic studies for more than a century. They have tremendous economic potential as a genetic mechanism for controlling pollination. Studies of these systems have contributed to a greater understanding of the process of fertilization, particularly with regard to interactions between pollen and silk. Three genetically distinct and functionally equivalent cross incompatibility systems exist in maize: Ga1, Tcb-1 and Ga2. These complex loci confer genetically separable functions to pollen and silk. Important advances in characterizing the genes involved in these systems in recent years. These studies reveal the importance of pectin methylesterase activity in controlling cross incompatibility systems by regulating the degree of methylesterification of the cell wall of the apex of the pollen tube, with interactions between pectin methylesterases and pectin methyesterase inhibitors present in pollen and silk controlling the level of pectin methylesterase activity. We present a molecular model that explains how cross incompatibility systems may function and is consistent with new information about the molecular characterization of the genes involved. This model is useful for testing hypotheses about uncharacterized cross incompatibility systems such as Ga2. Molecular characterization of these loci will allow researchers to bring new and powerful tools to bear on the problem of understanding gametophytic incompatibility systems of maize. We anticipate rapid progress in this area in the near future.