Genomic study reveals evolutionary secrets of banyan tree

Date:
October 8, 2020
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
The banyan fig tree Ficus microcarpa is famous for its aerial roots,
which sprout from branches and eventually reach the soil. The tree
also has a unique relationship with a wasp that has coevolved with
it and is the only insect that can pollinate it. In a new study,
researchers identify regions in the banyan fig's genome that
promote the development of its unusual aerial roots and enhance
its ability to signal its wasp pollinator.



FULL STORY ========================================================================== [Ficus microcarpa (stock | Credit: (c) Hatori_Shisuka / stock.adobe.com]
Ficus microcarpa (stock image).

Credit: (c) Hatori_Shisuka / stock.adobe.com [Ficus microcarpa (stock |
Credit: (c) Hatori_Shisuka / stock.adobe.com] Ficus microcarpa (stock
image).

Credit: (c) Hatori_Shisuka / stock.adobe.com Close The banyan fig tree
Ficus microcarpa is famous for its aerial roots, which sprout from
branches and eventually reach the soil. The tree also has a unique
relationship with a wasp that has coevolved with it and is the only
insect that can pollinate it.


==========================================================================
In a new study, researchers identify regions in the banyan fig's genome
that promote the development of its unusual aerial roots and enhance
its ability to signal its wasp pollinator.

The study, published in the journal Cell, also identifies a
sex-determining region in a related fig tree, Ficus hispida. Unlike
F. microcarpa, which produces aerial roots and bears male and female
flowers on the same tree, F.

hispida produces distinct male and female trees and no aerial roots.

Understanding the evolutionary history of Ficus species and their wasp pollinators is important because their ability to produce large fruits
in a variety of habitats makes them a keystone species in most tropical forests, said Ray Ming, a plant biology professor at the University
of Illinois, Urbana- Champaign who led the study with Jin Chen, of the
Chinese Academy of Sciences.

Figs are known to sustain at least 1,200 bird and mammal species. Fig
trees were among the earliest domesticated crops and appear as sacred
symbols in Hinduism, Buddhism and other spiritual traditions.

The relationship between figs and wasps also presents an intriguing
scientific challenge. The body shapes and sizes of the wasps correspond
exactly to those of the fig fruits, and each species of fig produces a
unique perfume to attract its specific wasp pollinator.

To better understand these evolutionary developments, Ming and his
colleagues analyzed the genomes of the two fig species, along with that
of a wasp that pollinates the banyan tree.

"When we sequenced the trees' genomes, we found more segmental
duplications in the genome of the banyan tree than in F. hispida, the
fig without the aerial roots," Ming said. "Those duplicated regions
account for about 27% of the genome." The duplications increased the
number of genes involved in the synthesis and transport of auxins, a
class of hormones that promote plant growth. The duplicated regions also contained genes involved in plant immunity, nutrition and the production
of volatile organic compounds that signal pollinators.

"The levels of auxin in the aerial roots are five times higher than
in the leaves of trees with or without aerial roots," Ming said. The
elevated auxin levels appear to have triggered aerial root production. The duplicated regions also include genes that code for a light receptor
that accelerates auxin production.

When they studied the genome of the fig wasp and compared it with those
of other related wasps, the researchers observed that the wasps were
retaining and preserving genes for odorant receptors that detect the
same smelly compounds the fig trees produce. These genomic signatures
are a signal of coevolution between the fig trees and the wasps, the researchers report.

Ming and his colleagues also discovered a Y chromosome-specific gene that
is expressed only in male plants of F. hispida and three other fig species
that produce separate male and female plants, a condition known as dioecy.

"This gene had been duplicated twice in the dioecious genomes, giving the plants three copies of the gene. But Ficus species that have male and
female flowers together on one plant have only one copy of this gene,"
Ming said.

"This strongly suggests that this gene is a dominant factor affecting
sex determination."

========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Diana Yates. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Xingtan Zhang, Gang Wang, Shengcheng Zhang, Shuai Chen, Yibin
Wang, Ping
Wen, Xiaokai Ma, Yan Shi, Rui Qi, Yang Yang, Zhenyang Liao, Jing
Lin, Jishan Lin, Xiuming Xu, Xuequn Chen, Xindan Xu, Fang Deng,
Lihua Zhao, Yi-lun Lee, Rong Wang, Xiao-Yong Chen, Yann-rong Lin,
Jisen Zhang, Haibao Tang, Jin Chen, Ray Ming. Genomes of the
Banyan Tree and Pollinator Wasp Provide Insights into Fig-Wasp
Coevolution. Cell, 2020; DOI: 10.1016/ j.cell.2020.09.043 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201008121248.htm

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