Lignin Biosynthesis in Postharvest Water Bamboo (<i>Zizania latifolia</i>) Shoots during Cold Storage Is Regulated by <i>RBOH</i>-Mediated Reactive Oxygen Species Signaling

Lignification is a major cause of senescence in fresh
shoots of
water bamboo (Zizania latifolia), which is a popular
vegetable in southeast Asia; however, its physiological and molecular
mechanisms is less understood. In the present study, lignin content
and transcriptome change in postharvested water bamboo shoots under
cold storage were investigated. We found that lignin significantly
accumulated in the epidermis of the shoots with the increase of firmness.
In the cold storage shoots, the major up-regulated genes were involved
in phenylpropanoid biosynthesis, plant-pathogen interactions, and
starch and sucrose metabolism. The lignin biosynthesis genes PAL, 4CL, C4H, CCoAOMT, CCR, F5H, CAD, and POD family were up-regulated during
cold storage, while HCT and C3H were
down-regulated. The MAPK signaling pathway was also up-regulated and respiratory burst oxidase homologue (RBOH) genes were strongly up-regulated. Therefore, we investigated the RBOH gene family and their expression profile in water bamboo
shoots. The results indicated that 10 ZlRBOHs were
up-regulated in cold storage shoots. Diphenyleneiodonium chloride
(DPI), an inhibitor of RBOH oxidase, significantly inhibited the expression
of genes involved in lignin deposition and biosynthesis, while H2O2 enhanced these processes. These results suggest
that lignification of water bamboo shoots is regulated by RBOH-mediated ROS signaling.