Abstract
In seed-bearing plants, the ovule (“small egg”) is the organ within the gynoecium that develops into a seed after fertilization. The gynoecium located in the inner compartment of the flower turns into a fruit. The number of ovules in the ovary determines the upper limit or the potential of seed number per fruit in plants, greatly affecting the final seed yield. Ovule number is an important adaptive characteristic for plant evolution and an agronomic trait for crop improvement. Therefore, understanding the mechanism and pathways of ovule number regulation becomes a significant research aspect in plant science. This review summarizes the ovule number regulators and their regulatory mechanisms and pathways. Specially, an integrated molecular network for ovule number regulation is constructed, in which phytohormones played a central role, followed by transcription factors, enzymes, other protein and micro-RNA. Of them, AUX, BR and CK are positive regulator of ovule number, whereas GA acts negatively on it. Interestingly, many ovule number regulators have conserved functions across several plant taxa, which should be the targets of genetic improvement via breeding or gene editing. Many ovule number regulators identified to date are involved in the diverse biological process, such as ovule primordia formation, ovule initiation, patterning, and morphogenesis. The relations between ovule number and related characteristics/traits especially of gynoecium/fruit size, ovule fertility, and final seed number, as well as upcoming research questions, are also discussed. In summary, this review provides a general overview of the present finding in ovule number regulation, which represents a more comprehensive and in-depth cognition on it.
Highlights
The reproductive organs formation and their meiocytes take place late during plant development, in contrast to animals where primordial germ cell development occurs during embryonic development [1,2]
Functional characterization of “ovule number controlling genes” shows that a significant number play a role in biosynthesis and signaling pathways of several types of phytohormones, mainly as auxins (AUX), cytokinins (CK), brassinosteroids (BR), and gibberellins (GA)
PAN is a bZIP transcription factor expressed in the gynoecium medial ridge and the placenta, where it stimulates the formation of ovules [31,33]
Summary
The reproductive organs formation and their meiocytes take place late during plant development, in contrast to animals where primordial germ cell development occurs during embryonic development [1,2]. Morphological, genetic, and molecular levels in Arabidopsis and other plant species [7– These studies show the formation of a completely developed set of ovules through several. Important genetic trait the plant mechanism of ovule number regulation has emerged as a significant research aspect in for evolution and crop improvement [20,21]. Analyses of mutants defective in ovule development have identified dozens of genes affecting ONPO, mainly from Arabidopsis, and in petunia, rice, tomato, and rapeseed [31] The summary of these ovule number genes, emphasizing their regulatory pathways and molecular mechanisms, will provide a comprehensive and in-depth understanding of ovule number regulation in plants. We give some creative suggestions and practical targets toward the molecular improvement of ovule numbers with technologies such as gene editing, which will be very useful for plant breeders
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
