The Role of Late-Acting Self-Incompatibility and Early-Acting Inbreeding Depression in Governing Female Fertility in Monkshood, Aconitum kusnezoffii

Yi-Qi Hao,Deng-Ying She,Xin-Feng Zhao,Da-Yong Zhang,Wan-Jin Liao,Bing Xu,Dmitry A Filatov

doi:10.1371/journal.pone.0047034

Yi-Qi Hao, Deng-Ying She + Show 5 more

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https://doi.org/10.1371/journal.pone.0047034

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Journal: PLoS ONE	Publication Date: Oct 9, 2012
Citations: 54	License type: CC BY 4.0

Affiliation: Beijing Normal University

Abstract

Reduced seed yields following self-pollination have repeatedly been observed, but the underlying mechanisms remain elusive when self-pollen tubes can readily grow into ovaries, because pre-, post-zygotic late-acting self-incompatibility (LSI), or early-acting inbreeding depression (ID) can induce self-sterility. The main objective of this study was to differentiate these processes in Aconitum kusnezoffii, a plant lacking stigmatic or stylar inhibition of self-pollination. We performed a hand-pollination experiment in a natural population of A. kusnezoffii, compared seed set among five pollination treatments, and evaluated the distribution of seed size and seed set. Embryonic development suggested fertilization following self-pollination. A partial pre-zygotic LSI was suggested to account for the reduced seed set by two lines of evidence. The seed set of chase-pollination treatment significantly exceeded that of self-pollination treatment, and the proportion of unfertilized ovules was the highest following self-pollination. Meanwhile, early-acting ID, rather than post-zygotic LSI, was suggested by the findings that the size of aborted selfed seeds varied continuously and widely; and the selfed seed set both exhibited a continuous distribution and positively correlated with the crossed seed set. These results indicated that the embryos were aborted at different stages due to the expression of many deleterious alleles throughout the genome during seed maturation. No signature of post-zygotic LSI was found. Both partial pre-zygotic LSI and early-acting ID contribute to the reduction in selfed seed set in A. kusnezoffii, with pre-zygotic LSI rejecting part of the self-pollen and early-acting ID aborting part of the self-fertilized seeds.

Highlights

Reduced female fertility following self-pollination is generally attributed to either self-incompatibility or early-acting inbreeding depression (ID)
We focused on two major questions: (1) does self-pollination lead to self-fertilization; and (2) is embryo abortion following self-pollination attributable to earlyacting inbreeding depression or post-zygotic self-incompatibility? We performed self, cross, chase, and mixed-pollinations in a single A. kusnezoffii population and used the five methods described above to distinguish between late-acting selfincompatibility (LSI) and ID
Pre- and/or Post-zygotic Process Serial sections of ovaries showed that zygotes have formed and begun to divide within 1 day after both self- and cross-pollination (Fig. 1)

Summary

Introduction

Reduced female fertility following self-pollination is generally attributed to either self-incompatibility or early-acting inbreeding depression (ID). For many plant species self-pollen tubes grow successfully in the styles and extend to the ovaries, implicating late-acting selfincompatibility (LSI) [4,5,6,7,8,9,10]. In such cases, the inhibition of self-pollen tubes could occur either pre-zygotically or postzygotically, which is commonly thought to be controlled by a single locus [5,9,10,11,12]. Early-acting ID acts postzygotically and leads to the abortion of developing embryos that are homozygous for many deleterious recessive alleles throughout the genome [15,16,17]

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