Wheat Information Service
Number 70: 7 - 10(1990)

Ribonuclease activity and soluble proteins in Lr isogenic lines of wheat (Triticum aestivum L.)

J. P. Sharma and H. S. Chawla

Plant Breeding Dept., G.B. Pant Univ. of Agric. & Tech., Pantnagar, U.P., 263145, India

Summary

Quantitative variation for soluble proteins and RNA degrading enzymes viz; ribonuclease I and ribonuclease II and nuclease I were studied in ten leaf rust isolines of wheat and two cultivars "Thatcher" and "Prelude" at early stages of germination. Crude seed extract showed maximum amount of soluble protein. Two distinct reductions at 24 hr and 96 hr stages were noticed for soluble proteins. Specific activity of RNase I and RNase II + Nu I showed a continuous increase upto 96 hr stage and then declined at one week stage. Specific pattern in reduction to ribonuclease and proteins for isogenic lines with or without Lr genes was not observed.

Introduction

Numerous biochemical changes accompany seed germination (Breevers 1968, Koller et al 1962). Proteins which are frequent reserve material in seed is mobilised and degraded in an ordered series of events. New proteins may be synthesised with advancement of germination (Hadwiger and Wagoner 1983). Ribonucleases are present in the resting seeds and their activity shows a steady rise on imbibition of water (Stern and Hotta 1963). High activity of plant ribonucleases has been correlated with pathogenesis (Chakravorty et al 1974).

Though studies have been conducted after pathogen infection yet there is little information about activities of ribonucleases in healthy plants which differ in their resistance to leaf rust. In present study soluble proteins and ribonucleases were studied in isogenic lines of wheat with leaf rust resistance (Lr) genes in different genetic backbrounds.

Material and Methods

Material consisted of ten isogenic lines of wheat with Lr genes in genetic backgrounds of "Thatcher" (Tc) and "Prelude" (Pr) and parental cultivars "Thatcher" and "Prelude". The entries were sequenced alphabetically as a) (Tc), b) (Pr), c) Lr1 (Tc), d) Lr1 (Pr), e) Lr3bg (Tc), f) Lr3ka (Tc), g) Lr3ka (Pr), h) Lr10 (Tc), i) Lr10(Pr), j)Lr16(Pr), k) Lr16(Pr), l) Lr-17 (Pr). Seeds were grown in petridishes in an incubator for different germination stages of 0, 24, 48, 72, 96 hrs and one week at a temperature of 25C. Sample material of each (2g) was homogenised in 3 ml acetate buffer (pH 5.2) and centrifuged at 12,000 x g for 20 min at 0C. Soluble proteins were estimated according to Braford (1976) using BSA as a standard. Ribonuclease I (RNase I) and combined ribonuclease II and nuclease I (RNase II + Nu I) activities were assayed by the procedure of Sodek and Wright (1969). Spectrophotometric readings were converted to standard units as described by Wilson (1975).