Fine Mapping of a Novel Major Quantitative Trait Locus, qPAA7, That Controls Panicle Apical Abortion in Rice

Identification and characterization of genes for drought tolerance in upland rice cultivar 'Banglami' of North East India

INTRODUCTION

Rice is a major crop in Assam, North East (NE) India. The rice accessions belonging to NE India possess unique traits of breeder's interest, i.e., tolerant to biotic and abiotic stresses. In the present research programme, the stress responsive genes were identified within the QTLs associated with drought tolerance. The differential expression profiling of genes were performed under drought stress and control conditions. Thus, the 'candidate genes' associated with drought tolerance were recognised and may be deployed in a breeding programme.

METHODS AND RESULTS

A drought-tolerant traditional rice cultivar, Banglami, was crossed with a high-yielding, drought-susceptible variety, Ranjit. The mapping population (F₄) was raised through the single seed descent (SSD) method and used in QTL analysis. Under drought stress, a total of 4752 genes were identified through in-silico mining of QTLs. Among these, only 21 genes primarily associated with the stress response. The maximum of four stress-responsive genes were located within the QTLs, qNOG12.1 and qGY1.1. However, under control conditions, 2088 genes were identified, out of which, only 15 were categorised as the major stress responsive genes. The functional characterization of genes recognized 24 different types of proteins. Among these, peroxidase and heat shock proteins (Hsp) are the principal proteins encoded during stress. In addition to that, OsbZIP23, inorganic pyrophosphatase, universal stress protein, serine threonine kinase, NADPH oxidoreductase, and proteins belonging to the ABC1 family were also produced during stress condition. The differential expression profiling showed a profound expression pattern of three candidate genes under drought stress condition, i.e., OsI_32199 (Ascorbate peroxidase), OsI_37694 (Universal stress protein) and OsI_32167 (Heat shock protein 81 - 1).

CONCLUSION

The novel candidate genes identified for drought tolerance, may be used in the breeding programme for the development of 'climate smart rice varieties'.

LMPA Regulates Lesion Mimic Leaf and Panicle Development Through ROS-Induced PCD in Rice

Leaf and panicle are important nutrient and yield organs in rice, respectively. Although several genes controlling lesion mimic leaf and panicle abortion have been identified, a few studies have reported the involvement of a single gene in the production of both the traits. In this study, we characterized a panicle abortion mutant, lesion mimic leaf and panicle apical abortion (lmpa), which exhibits lesions on the leaf and causes degeneration of apical spikelets. Molecular cloning revealed that LMPA encodes a proton pump ATPase protein that is localized in the plasma membrane and is highly expressed in leaves and panicles. The analysis of promoter activity showed that the insertion of a fragment in the promoter of lmpa caused a decrease in the transcription level. Cellular and histochemistry analysis indicated that the ROS accumulated and cell death occurred in lmpa. Moreover, physiological experiments revealed that lmpa was more sensitive to high temperatures and salt stress conditions. These results provide a better understanding of the role of LMPA in panicle development and lesion mimic formation by regulating ROS homeostasis.