Reference "Saturation mapping of QTL regions and identification of putative candidate genes for drought tolerance in rice"

Reference ID

8314

Title

Saturation mapping of QTL regions and identification of putative candidate genes for drought tolerance in rice

Source

Mol Genet Genomics, 2004, vol. , pp. -

Authors (8)

Nguyen-T-T	Klueva-N
Chamareck-V	Aarti-A
Magpantay-G	Millena-A-C
Pathan-M-S	Nguyen-H-T

Abstract

We have developed 85 new markers (50 RFLPs, 5 SSRs, 12 DD cDNAs, 9 ESTs, 8 HSP-
encoding cDNAs and one BSA-derived AFLP marker) for saturation mapping of QTL
regions for drought tolerance in rice, in our efforts to identify putative
candidate genes. Thirteen of the markers were localized in the close vicinity of
the targeted QTL regions. Fifteen of the additional markers mapped,
respectively, inside one QTL region controlling osmotic adjustment on chromosome
3 ( oa3.1) and 14 regions that affect root traits on chromosomes 1, 2, 4, 5, 6,
7, 8, 9, 10 and 12. Differential display was used to identify more putative
candidate genes and to saturate the QTL regions of the genetic map. Eleven of
the isolated cDNA clones were found to be derived from drought-inducible genes.
Two of them were unique and did not match any genes in the GenBank, while nine
were highly similar to cDNAs encoding known proteins, including a DnaJ-related
protein, a zinc-finger protein, a protease inhibitor, a glutathione-S-
transferase, a DNA recombinase, and a protease. Twelve new cDNA fragments were
mapped onto the genetic linkage map; seven of these mapped inside, or in close
proximity to, the targeted QTL regions determining root thickness and osmotic
adjustment capacity. The gene I12A1, which codes for a UDP-glucose 4-epimerase
homolog, was identified as a putative target gene within the prt7.1/brt7.1 QTL
region, as it is involved in the cell wall biogenesis pathway and hence may be
implicated in modulating the ability of rice roots to penetrate further into the
substratum when exposed to drought conditions. RNAs encoding elongation factor
1beta, a DnaJ-related protein, and a homolog of wheat zinc-finger protein were
more prominently induced in the leaves of IR62266 (the lowland rice parent of
the mapping materials used) than in those of CT9993 (the upland rice parent)
under drought conditions. Homologs of 18S ribosomal RNA, and mRNAs for a multiple-
stress induced zinc-finger protein, a protease inhibitor, and a glutathione-S-
transferase were expressed at significantly higher levels in CT9993 than in
IR62266. Thus several genes involved in the regulation of DNA structure and mRNA
translation were found to be drought-regulated, and may be implicated in drought
resistance.