February 2022: Abscisic acid and proline are not equivalent markers for heat & drought

Dear PhotosynQ User, Welcome to the PhotosynQ community newsletter! We have the following study by Lehr et al. (2021) as our featured project this month. This project corresponds well with PhotosynQ's vision of using chlorophyll fluorescence parameters to screen stress status and tolerance of important crops. We hope you enjoy reading our selected study and please stay safe and healthy! Best, PhotosynQ Team

P.P. Lehr, E. Hernandez-Montes, J. Ludwig-Müller, M. Keller and C. Zörb

Abscisic acid and proline are not equivalent markers for heat, drought, and combined stress in grapevines

Australian Journal of Grape and Wine Research https://doi.org/10.1111/ajgw.12523

This study investigated proline and abscisic acid accumulations as biomarkers for heat, drought, or combined stress and the regulation of gene expression of key enzymes in abscisic acid biosynthesis in grapevine leaves under heat and drought.

The authors used MultispeQ to record chlorophyll fluorescence measurements of grapevine leaves along with stomatal conductance, photosynthetic rate, leaf temperature, & transpiration rate after 7 days of subjecting plants to various stressors.

Figure 1. PC bi-plot from the Principal Component Analysis (PCA) of shoot growth, stomatal conductance, photosynthetic rate, leaf temperature, transpiration rate, chlorophyll fluorescence, concentration of abscisic acid (ABA) and proline and gene expression analysis of the genes NCED1, NCED2 and P5CS in response to four treatments on two grape cultivars.

According to Figure 1 (above) and Figure 2 (below),

PhiNPQ is correlated with expression of P5CS and in proline concertation

Phi2 and PhiNO are correlated with photosynthetic rate, stomatal conductance, transpiration rate, and growth

These results demonstrate the applicability of employing PhiNPQ, Phi2, and PhiNO as biomarkers for screening towards heat and drought tolerance.

Figure 2. Pearson correlation coefficients (PCC) calculated for pairwise traits: shoot growth, stomatal conductance, photosynthetic rate, leaf temperature, transpiration rate, chlorophyll fluorescence, concentration of abscisic acid (ABA) and proline and gene expression analysis of the genes NCED1, NCED2 and P5CS. Size of circle and color indicates the magnitude and the direction of correlation. Cross represents non-significant correlation (P = 0.05).

This study highlights the correlation of MultispeQ-derived chlorophyll fluorescence parameters with the well known biomarkers for screening crop plants towards heat and drought.

Breeding programs can employ this technology as a phenomic tool to strengthen the marker assisted selection to expedite the varietal selection process.