Understanding self and non-self root-root interaction on root system architecture and expression of putative nitrate transceptor gene in bread wheat under nitrogen limited condition
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Date
2020
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Division of Molecular Biology and Biotechnology ICAR-Indian agricultural research institute New delhi
Abstract
Roots are one of the most important plant organ for its life. It helps in acquisition of nutrients
and water from soil. One of the major reasons of roots to modulate its architecture is due to the
recognition of kin (self) and non-kin (non-self) root growing together in one soil volume. Roots
recognizes kin plant by “Identity Recognition”. Weed appears as non-kin plants to crop plants in
agricultural field. After green revolution, farmers started cultivating the high yielding wheat
varieties on commercially basis. These varieties are less competitive and demands high inputs
(irrigation and fertilizers). As favorable micro-environment being made available due to the
application of high amount of nitrogenous fertilizers, it leads to the increased weed infestation,
and consequently Phalaris minor evolved as one of the major weed in rice-wheat growing tract
during 1970s. P. minor causes yield reduction by 20-30% and in severe cases complete crop
failure may also occur. On the contrary, the nitrogen use efficiency (NUE) of wheat is abysmally
low. Only 30-35% of applied nitrogen is taken up by the wheat plants and rest 65-70% is lost to
environment in various form. It is reported that P. minor can deplete 28 kg/ha nitrogen from
wheat field. According to one survey world population is projected to be 9 billion by 2050,
which will necessitate additional application of nitrogen (N) fertilizers to support production of
additional biomass and grains. Wheat improvement programs, therefore, has now focusing also
on enhancing nitrogen use efficiency (NUE) trait of wheat including other traits. In Arabidopsis,
AtNRT1.1 has been reported as nitrate transceptor, i.e., functions as both receptor and transceptor
of nitrate molecule. It is a dual affinity nitrate transporter, i.e., it can transport nitrate when it is
present in low as well as high concentration in external medium. Also, AtNRT1.1 plays several
role, e.g., auxin signalling, lateral root development etc. Therefore, considering its transceptor
activity, it is hypotheiszed that its ortholog may play some role in lateral root
elongation/differentiation in wheat in the presence of one of its major weeds, i.e., P. minor. Here
in this study, I report self and non-self root-root interaction on root system architecture and
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expression of putative nitrate transceptor gene in bread wheat ((Triticum aestivum L) under
nitrogen limited condition.
In the present study, it has been found that P. minor has profound effect on root system
architecture, biomass and nitrogen uptake ability of wheat in nitrogen limited condition. Root
biomass (length, fresh and dry weight) of wheat invariably increased under N-starvation
condition which further increased when P. minor is present in the same condition. To
compensate the increased growth of root system, the corresponding parameters of shoot has been
found to be reduced. The growth of root was furthest corroborated by changes in its architecture
under these conditions. Both length-based root traits, e.g., TRS, MRP and LRS, as well as
numbers-based traits, e.g., first and second order lateral root numbers have been found to be
increased by the presence of P. minor, specially under N-starved condition.
AtNRT1.1 (At1g12110) sequence is first used as seed sequence to identify the orthologs in
wheat. 13 orthologs have been identified in wheat in wheat genomes located in 1
st
, 2
nd
, 4
th
, 5
th
and 7
th chromosomes of all three sub-genomes. In order to precisely identify the putative nitrate
transceptor in wheat, rice nitrate transceptor (NRT1.1B) was used to identify the closest
sequence(s) among 13 identified from Arabidopsis. Based on the phylogenetic analysis, 4 closest
sequences were selected as putative nitrate transceptor of wheat (TaNPF6.4), located in 4th
, 5
th
and 7
th chromosome. These sequences were also reported to be closet orthologs of AtNRT1.1.The
homeolog specific expression of TaNRT1.1 (TaNPF6.4) in wheat genotype K9107 reveals that
sub-genome A is highest expressing homeolog in both seminal and lateral roots. In order to
understand the mechanism of different expression pattern of these four homeologs under
different conditions in the present study, 2Kb upstream sequences of all three homeologues were
cloned analyzed bioinformatically. The upstream sequences of homeologs revealed variation in
number of CREs.
Key words:Wheat, NRT1.1, Nitrate tranceptor, Phalaris minor, nitrogen use efficiency
Description
T-10314