Researchers discover when pollen comes of age

Date:
February 22, 2022
Source:
University of Georgia
Summary:
It cakes our cars in yellow powder every spring and taunts allergy
sufferers for months on end, but pollen is more than just plant
sperm.

New research has determined when pollen comes of age and begins
expressing its own genome, a major life cycle transition in plants.



FULL STORY ==========================================================================
It cakes our cars in yellow powder every spring and taunts allergy
sufferers for months on end, but pollen is more than just plant sperm.


==========================================================================
New research from the University of Georgia has determined when pollen
comes of age and begins expressing its own genome, a major life cycle transition in plants.

Each grain of pollen is actually its own multicellular organism --
with two to 40 cells, depending on the species. Pollen expresses its
own genome and is genetically distinct from its parent plant. That
means pollen grains from a single flower can have different traits and characteristics, similar to how you might be different from your siblings.

When pollen grains compete to fertilize the egg, only those pollen grains
with the most successful traits will survive to pass on their genetic information to the next generation. This fierce competition between pollen
is a quality check on the genome in plants because harmful mutations
are removed when the pollen grains with these mutations cannot compete.

Before the study, which landed the Jan. 28 cover of Science, scientists
weren't sure when pollen began to express its own genetic information.

"Since pollen expresses its own genome, natural selection can act
directly on pollen. This makes pollen competition an important force
shaping plant evolution," said Brad Nelms, lead author of the study and
an assistant professor of plant biology in the Franklin College of Arts
and Sciences. "If we had better knowledge of the extent and timing of
pollen selection, it would help us better predict how plant species adapt
to changing environments. We might even be able to use pollen selection
to speed up crop breeding, selecting for more heat-tolerant crops,
for example." The 'hidden life' of pollen Pollen selection is key to successful breeding. But pollen development is incredibly vulnerable to
heat stress.

Rising temperatures can cause irreversible damage to the plants themselves
and can also alter how much pollen is produced by a given plant. In
turn, that coupled with other heat-induced changes to a plant's sexual reproductive cycle can ultimately lead to lower crop yields, a major
concern for food security.

"For instance, all the starches that are made in grains are also made
in pollen," Nelms said. "The same pathways are there. So we're figuring
out ways where we can actually do loss of function genetics directly
on pollen." The researchers sequenced RNA content from maize pollen
cells for 26 days, beginning with the formation of spores in a process
known as meiosis, and ending with fully formed pollen detaching from
its parent plant.

"What a lot of people think about when we think of pollen is
once we see a flower and you see the pollen about to be shed, but
pollen development actually begins really early in the flower,"
Nelms said. "In corn, for instance, I plant a seed in the ground,
and five or six weeks later, the plant would come up to around
my chest. You wouldn't see any signs of flowering yet, but those
organisms are already growing deep inside the plant. It's this kind
of complex hidden process that we hadn't seen much before in plants." ========================================================================== Story Source: Materials provided by University_of_Georgia. Original
written by Leigh Beeson.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Brad Nelms, Virginia Walbot. Gametophyte genome activation occurs at
pollen mitosis I in maize. Science, 2022; 375 (6579): 424 DOI:
10.1126/ science.abl7392 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220222121234.htm

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