Abstract
Self-incompatibility (SI) is a widespread prezygotic mechanism for flowering plants to avoid inbreeding depression and promote genetic diversity. Citrus has an S-RNase-based SI system, which was frequently lost during evolution. We previously identified a single nucleotide mutation in Sm-RNase, which is responsible for the loss of SI in mandarin and its hybrids. However, little is known about other mechanisms responsible for conversion of SI to self-compatibility (SC) and we identify a completely different mechanism widely utilized by citrus. Here, we found a 786-bp miniature inverted-repeat transposable element (MITE) insertion in the promoter region of the FhiS2-RNase in Fortunella hindsii Swingle (a model plant for citrus gene function), which does not contain the Sm-RNase allele but are still SC. We demonstrate that this MITE plays a pivotal role in the loss of SI in citrus, providing evidence that this MITE insertion prevents expression of the S-RNase; moreover, transgenic experiments show that deletion of this 786-bp MITE insertion recovers the expression of FhiS2-RNase and restores SI. This study identifies the first evidence for a role for MITEs at the S-locus affecting the SI phenotype. A family-wide survey of the S-locus revealed that MITE insertions occur frequently adjacent to S-RNase alleles in different citrus genera, but only certain MITEs appear to be responsible for the loss of SI. Our study provides evidence that insertion of MITEs into a promoter region can alter a breeding strategy and suggests that this phenomenon may be broadly responsible for SC in species with the S-RNase system.
Original language | English |
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Journal | Plant Biotechnology Journal |
Early online date | 1 Dec 2023 |
DOIs | |
Publication status | E-pub ahead of print - 1 Dec 2023 |
Bibliographical note
Research Funding:Agriculture Research System of China. Grant Number: CARS-26
Hubei Provincial Natural Science Foundation of China. Grant Number: 2023AFB094
Key-Area Research and Development Program of Guangdong Province. Grant Number: 2022B0202070002
National Key Research and Development Program of China. Grant Number: 2021YFD1200200
National Natural Science Foundation of China. Grant Numbers: 32270357, 32072523, 32122075, 32302489