Identification and characterization of high temperature stress responsive genes in maize (Zea mays L.)
Loading...
Date
2020
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Punjab Agricultural University, Ludhiana
Abstract
Heat stress due to climate change is an emerging issue for maize breeders as it largely affects the
yield. The present study focuses to elucidate molecular mechanisms and underlying genes, or QTLs
associated with heat stress tolerance in maize. The transcriptional studies of maize leaves, pollens
and ovules using heat stress susceptible and tolerant inbred lines, namely LM11 and CML25,
respectively revealed a total of 2,164 (1127 up-regulated and 1037 down-regulated) differentially
expressed genes (DEGs) between LM11 (HS) and CML25 (HT) samples, with 1151, 451 and 562
DEGs were identified in comparisons of corresponding leaf, pollen and ovule samples, respectively.
Functional annotations of DEGs showed that many of them were related to transcription factors
(TFs) viz. AP2, MYB, WRKY, PsbP, bZIP and NAM, heat shock proteins (HSP20, HSP70 and
HSP101/ClpB), as well as genes related to photosynthesis (PsaD and PsaN), antioxidation (APX
and CAT) and polyamines (Spd and Spm). KEGG pathways analyses explicated that metabolic
overview pathway and secondary metabolites biosynthesis pathway, with involvement of 264 and
146 genes, respectively were highly enriched in response to heat stress. A bioinformatics pipeline
was used to call and type SNPs from RNA-seq reads and applied it to transcriptomic data of LM11
and CML25. A total of 554,423, 410,698 and 596,868 polymorphic SNPs were identified
respectively among leaf, pollen and ovule of the LM11 and CML25. A total of 100 genome-wide
SNP based KASP assay markers were developed and validated as well as subsequently genotyped
on 90 F2 individuals derived from the cross of LM11 × CML25. The success of SNP conversion rate
was 71%. In addition, F2 population and their parental inbreds were genotyped using 94
polymorphic SSR markers. The 175 F2:3 families during late March (Spring 2017) were evaluated
for heat stress under field and glass house conditions. Heat stress significantly affected all the
morpho-physiological and yield contributing traits. Grain yield was positively associated with ear
weight, number of kernels per ear, pollen viability, pollen shedding durations and chlorophyll
content. Furthermore, secondary traits like membrane thermostability, days to anthesis and silking,
anthesis-silking interval, canopy temperature, leaf firing and tassel blast showed significant negative
impact on grain yield in both field and glass house conditions under heat stress. Both genotyping
and mean phenotypic data of each component trait was analyzed for single marker analysis (SMA)
and composite interval mapping (CIM) using WinQTL Cartographer. A linkage map of 1857.1 cM
in total length was constructed by applying both SSR and SNP markers. A total of 11 QTLs were
detected for 7 traits on chromosomes 1, 3, 4, 6, 7 and 9 with phenotypic variance ranged from 8.67
to 29.62 per cent. Four of these QTLs, qKPE6.1, qPV6.1, qCC9.2 and qLF4.1, accounted for above
15 per cent of phenotypic variation, and might be considered as major QTLs for heat tolerance. The
data generated in present investigation laid the foundation for future work to uncover genes and
mechanisms critical for the development of heat-resilient maize using genetic and biotechnological
approaches.
Description
Keywords
Citation
Ashok Babadev Jagtap (2020). Identification and characterization of high temperature stress responsive genes in maize (Zea mays L.) (Unpublished Ph.D. Dissertation) Punjab Agricultural University, Ludhiana, Punjab, India.